XenForo before 2.3.13 contains an uncontrolled recursion vulnerability in the BBCode parser that allows authenticated attackers to cause per…

cve CVE-2026-73321 1 source, 1 claim · Watch

NVD writes:
XenForo before 2.3.13 contains an uncontrolled recursion vulnerability in the BBCode parser that allows authenticated attackers to cause persistent denial of service by submitting a post with deeply nested BBCode tags. Attackers can craft a single malicious post with sufficient nesting depth to exceed PHP's stack limit, causing fatal errors that repeatedly terminate PHP-FPM workers for all visitors rendering the affected thread. the claim

Severity: MEDIUM NVD
CVSS: 6.5 NVD
Fixed in: 2.3.13 NVD
Vendor: XenForo NVD
Product: XenForo NVD
CWE: CWE-674 NVD

How far exploitation has got

No public code known
Proof of concept
Proof of concept, verified
A Metasploit module
Exploited in the wild
Used in ransomware campaigns

Timeline

2026-09-08

first spoke of it: XenForo before 2.3.13 contains an uncontrolled recursion vulnerability in the BBCode parser that allows authenticated attackers to cause persistent denial of service by submitting a post with deeply nested BBCode tags. Attackers can craft a single malicious post with sufficient nesting depth to exceed PHP's stack limit, causing fatal errors that repeatedly terminate PHP-FPM workers for all visitors rendering the affected thread.

NVD

XenForo before 2.3.13 contains an uncontrolled recursion vulnerability in the BBCode parser that allows authenticated attackers to cause persistent denial of service by submitting a post with deeply nested BBCode tags. Attackers can craft a single malicious post with sufficient nesting depth to exceed PHP's stack limit, causing fatal errors that repeatedly terminate PHP-FPM workers for all visitors rendering the affected thread.

What it is to other things

affects	xenforo/xenforo NVD
made_by	xenforo NVD

Every value, with what each source said and its receipt

Property Source Said Means here

Automatable

automatable

NVD

At least one of those steps needs a person.

receipt

Source: NVD
Its words: no
Read by: field:cve.metrics.ssvcV203[].ssvcData.options[].automatable
Said since: 2026-10-06 12:31 UTC
Last answered: 2026-10-06 12:41 UTC
Original: open at the source

2026-10-06 12:31 UTC	no
2026-09-29 09:45 UTC	—

What the source handed over

{
  "cve": {
    "affected": [
      {
        "affectedData": [
          {
            "defaultStatus": "unaffected",
            "product": "XenForo",
            "vendor": "XenForo",
            "versions": [
              {
                "lessThan": "2.3.13",
                "status": "affected",
                "version": "0",
                "versionType": "semver"
              }
            ]
          }
        ],
        "source": "disclosure@vulncheck.com"
      }
    ],
    "configurations": [
      {
        "nodes": [
          {
            "cpeMatch": [
              {
                "criteria": "cpe:2.3:a:xenforo:xenforo:*:*:*:*:*:*:*:*",
                "matchCriteriaId": "DD926609-EB0D-4EED-B36A-D482E4B5FDDC",
                "versionEndExcluding": "2.3.13",
                "vulnerable": true
              }
            ],
            "negate": false,
            "operator": "OR"
          }
        ]
      }
    ],
    "cveTags": [],
    "descriptions": [
      {
        "lang": "en",
        "value": "XenForo before 2.3.13 contains an uncontrolled recursion vulnerability in the BBCode parser that allows authenticated attackers to cause persistent denial of service by submitting a post with deeply nested BBCode tags. Attackers can craft a single malicious post with sufficient nesting depth to exceed PHP's stack limit, causing fatal errors that repeatedly terminate PHP-FPM workers for all visitors rendering the affected thread."
      }
    ],
    "id": "CVE-2026-73321",
    "lastModified": "2026-09-11T20:30:18.293",
    "metrics": {
      "cvssMetricV31": [
        {
          "cvssData": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 6.5,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "NONE",
            "integrityImpact": "NONE",
            "privilegesRequired": "LOW",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
            "version": "3.1"
          },
          "exploitabilityScore": 2.8,
          "impactScore": 3.6,
          "source": "disclosure@vulncheck.com",
          "type": "Secondary"
        }
      ],
      "cvssMetricV40": [
        {
          "cvssData": {
            "Automatable": "NOT_DEFINED",
            "Recovery": "NOT_DEFINED",
            "Safety": "NOT_DEFINED",
            "attackComplexity": "LOW",
            "attackRequirements": "NONE",
            "attackVector": "NETWORK",
            "availabilityRequirement": "NOT_DEFINED",
            "baseScore": 7.1,
            "baseSeverity": "HIGH",
            "confidentialityRequirement": "NOT_DEFINED",
            "exploitMaturity": "NOT_DEFINED",
            "integrityRequirement": "NOT_DEFINED",
            "modifiedAttackComplexity": "NOT_DEFINED",
            "modifiedAttackRequirements": "NOT_DEFINED",
            "modifiedAttackVector": "NOT_DEFINED",
            "modifiedPrivilegesRequired": "NOT_DEFINED",
            "modifiedSubAvailabilityImpact": "NOT_DEFINED",
            "modifiedSubConfidentialityImpact": "NOT_DEFINED",
            "modifiedSubIntegrityImpact": "NOT_DEFINED",
            "modifiedUserInteraction": "NOT_DEFINED",
            "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
            "modifiedVulnConfidentialityImpact": "NOT_DEFINED",
            "modifiedVulnIntegrityImpact": "NOT_DEFINED",
            "privilegesRequired": "LOW",
            "providerUrgency": "NOT_DEFINED",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "NONE",
            "userInteraction": "NONE",
            "valueDensity": "NOT_DEFINED",
            "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
            "version": "4.0",
            "vulnAvailabilityImpact": "HIGH",
            "vulnConfidentialityImpact": "NONE",
            "vulnIntegrityImpact": "NONE",
            "vulnerabilityResponseEffort": "NOT_DEFINED"
          },
          "source": "disclosure@vulncheck.com",
          "type": "Secondary"
        }
      ],
      "ssvcV203": [
        {
          "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "ssvcData": {
            "id": "CVE-2026-73321",
            "options": [
              {
                "exploitation": "poc"
              },
              {
                "automatable": "no"
              },
              {
                "technicalImpact": "partial"
              }
            ],
            "role": "CISA Coordinator",
            "timestamp": "2026-09-10T13:49:59.215010Z",
            "version": "2.0.3"
          }
        }
      ]
    },
    "published": "2026-09-08T14:17:26.617",
    "references": [
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Exploit",
          "Third Party Advisory"
        ],
        "url": "https://bombobombone.github.io/posts/cve-2026-73321/"
      },
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Exploit",
          "Third Party Advisory"
        ],
        "url": "https://github.com/BomboBombone/CVE-2026-73321"
      },
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Third Party Advisory"
        ],
        "url": "https://www.vulncheck.com/advisories/xenforo-uncontrolled-recursion-dos-via-bbcode-parser"
      },
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Release Notes"
        ],
        "url": "https://xenforo.com/community/threads/security-fixes-released-for-all-xenforo-and-media-gallery-versions-2-2-0-2-3-12.239856/"
      },
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Release Notes"
        ],
        "url": "https://xenforo.com/community/threads/xenforo-2-3-13-and-add-ons-released-includes-security-fixes.239857/"
      }
    ],
    "sourceIdentifier": "disclosure@vulncheck.com",
    "vulnStatus": "Analyzed",
    "weaknesses": [
      {
        "description": [
          {
            "lang": "en",
            "value": "CWE-674"
          }
        ],
        "source": "disclosure@vulncheck.com",
        "type": "Secondary"
      }
    ]
  }
}

—

CVSS

cvss

NVD

6.5

receipt

Source: NVD
Its words: 6.5
Read by: field:cve.metrics.cvssMetricV31[type=Primary].cvssData.baseScore || field:cve.metrics.cvssMetricV31[].cvssData.baseScore
Said since: 2026-09-29 09:45 UTC
Last answered: 2026-10-06 12:41 UTC
Original: open at the source

What the source handed over

{
  "cve": {
    "affected": [
      {
        "affectedData": [
          {
            "defaultStatus": "unaffected",
            "product": "XenForo",
            "vendor": "XenForo",
            "versions": [
              {
                "lessThan": "2.3.13",
                "status": "affected",
                "version": "0",
                "versionType": "semver"
              }
            ]
          }
        ],
        "source": "disclosure@vulncheck.com"
      }
    ],
    "configurations": [
      {
        "nodes": [
          {
            "cpeMatch": [
              {
                "criteria": "cpe:2.3:a:xenforo:xenforo:*:*:*:*:*:*:*:*",
                "matchCriteriaId": "DD926609-EB0D-4EED-B36A-D482E4B5FDDC",
                "versionEndExcluding": "2.3.13",
                "vulnerable": true
              }
            ],
            "negate": false,
            "operator": "OR"
          }
        ]
      }
    ],
    "cveTags": [],
    "descriptions": [
      {
        "lang": "en",
        "value": "XenForo before 2.3.13 contains an uncontrolled recursion vulnerability in the BBCode parser that allows authenticated attackers to cause persistent denial of service by submitting a post with deeply nested BBCode tags. Attackers can craft a single malicious post with sufficient nesting depth to exceed PHP's stack limit, causing fatal errors that repeatedly terminate PHP-FPM workers for all visitors rendering the affected thread."
      }
    ],
    "id": "CVE-2026-73321",
    "lastModified": "2026-09-11T20:30:18.293",
    "metrics": {
      "cvssMetricV31": [
        {
          "cvssData": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 6.5,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "NONE",
            "integrityImpact": "NONE",
            "privilegesRequired": "LOW",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
            "version": "3.1"
          },
          "exploitabilityScore": 2.8,
          "impactScore": 3.6,
          "source": "disclosure@vulncheck.com",
          "type": "Secondary"
        }
      ],
      "cvssMetricV40": [
        {
          "cvssData": {
            "Automatable": "NOT_DEFINED",
            "Recovery": "NOT_DEFINED",
            "Safety": "NOT_DEFINED",
            "attackComplexity": "LOW",
            "attackRequirements": "NONE",
            "attackVector": "NETWORK",
            "availabilityRequirement": "NOT_DEFINED",
            "baseScore": 7.1,
            "baseSeverity": "HIGH",
            "confidentialityRequirement": "NOT_DEFINED",
            "exploitMaturity": "NOT_DEFINED",
            "integrityRequirement": "NOT_DEFINED",
            "modifiedAttackComplexity": "NOT_DEFINED",
            "modifiedAttackRequirements": "NOT_DEFINED",
            "modifiedAttackVector": "NOT_DEFINED",
            "modifiedPrivilegesRequired": "NOT_DEFINED",
            "modifiedSubAvailabilityImpact": "NOT_DEFINED",
            "modifiedSubConfidentialityImpact": "NOT_DEFINED",
            "modifiedSubIntegrityImpact": "NOT_DEFINED",
            "modifiedUserInteraction": "NOT_DEFINED",
            "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
            "modifiedVulnConfidentialityImpact": "NOT_DEFINED",
            "modifiedVulnIntegrityImpact": "NOT_DEFINED",
            "privilegesRequired": "LOW",
            "providerUrgency": "NOT_DEFINED",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "NONE",
            "userInteraction": "NONE",
            "valueDensity": "NOT_DEFINED",
            "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
            "version": "4.0",
            "vulnAvailabilityImpact": "HIGH",
            "vulnConfidentialityImpact": "NONE",
            "vulnIntegrityImpact": "NONE",
            "vulnerabilityResponseEffort": "NOT_DEFINED"
          },
          "source": "disclosure@vulncheck.com",
          "type": "Secondary"
        }
      ],
      "ssvcV203": [
        {
          "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "ssvcData": {
            "id": "CVE-2026-73321",
            "options": [
              {
                "exploitation": "poc"
              },
              {
                "automatable": "no"
              },
              {
                "technicalImpact": "partial"
              }
            ],
            "role": "CISA Coordinator",
            "timestamp": "2026-09-10T13:49:59.215010Z",
            "version": "2.0.3"
          }
        }
      ]
    },
    "published": "2026-09-08T14:17:26.617",
    "references": [
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Exploit",
          "Third Party Advisory"
        ],
        "url": "https://bombobombone.github.io/posts/cve-2026-73321/"
      },
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Exploit",
          "Third Party Advisory"
        ],
        "url": "https://github.com/BomboBombone/CVE-2026-73321"
      },
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Third Party Advisory"
        ],
        "url": "https://www.vulncheck.com/advisories/xenforo-uncontrolled-recursion-dos-via-bbcode-parser"
      },
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Release Notes"
        ],
        "url": "https://xenforo.com/community/threads/security-fixes-released-for-all-xenforo-and-media-gallery-versions-2-2-0-2-3-12.239856/"
      },
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Release Notes"
        ],
        "url": "https://xenforo.com/community/threads/xenforo-2-3-13-and-add-ons-released-includes-security-fixes.239857/"
      }
    ],
    "sourceIdentifier": "disclosure@vulncheck.com",
    "vulnStatus": "Analyzed",
    "weaknesses": [
      {
        "description": [
          {
            "lang": "en",
            "value": "CWE-674"
          }
        ],
        "source": "disclosure@vulncheck.com",
        "type": "Secondary"
      }
    ]
  }
}

—

Cvss4

cvss4

NVD

7.1

receipt

Source: NVD
Its words: 7.1
Read by: field:cve.metrics.cvssMetricV40[type=Primary].cvssData.baseScore || field:cve.metrics.cvssMetricV40[].cvssData.baseScore
Said since: 2026-10-06 12:31 UTC
Last answered: 2026-10-06 12:41 UTC
Original: open at the source

2026-10-06 12:31 UTC	7.1
2026-09-29 09:45 UTC	—

What the source handed over

{
  "cve": {
    "affected": [
      {
        "affectedData": [
          {
            "defaultStatus": "unaffected",
            "product": "XenForo",
            "vendor": "XenForo",
            "versions": [
              {
                "lessThan": "2.3.13",
                "status": "affected",
                "version": "0",
                "versionType": "semver"
              }
            ]
          }
        ],
        "source": "disclosure@vulncheck.com"
      }
    ],
    "configurations": [
      {
        "nodes": [
          {
            "cpeMatch": [
              {
                "criteria": "cpe:2.3:a:xenforo:xenforo:*:*:*:*:*:*:*:*",
                "matchCriteriaId": "DD926609-EB0D-4EED-B36A-D482E4B5FDDC",
                "versionEndExcluding": "2.3.13",
                "vulnerable": true
              }
            ],
            "negate": false,
            "operator": "OR"
          }
        ]
      }
    ],
    "cveTags": [],
    "descriptions": [
      {
        "lang": "en",
        "value": "XenForo before 2.3.13 contains an uncontrolled recursion vulnerability in the BBCode parser that allows authenticated attackers to cause persistent denial of service by submitting a post with deeply nested BBCode tags. Attackers can craft a single malicious post with sufficient nesting depth to exceed PHP's stack limit, causing fatal errors that repeatedly terminate PHP-FPM workers for all visitors rendering the affected thread."
      }
    ],
    "id": "CVE-2026-73321",
    "lastModified": "2026-09-11T20:30:18.293",
    "metrics": {
      "cvssMetricV31": [
        {
          "cvssData": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 6.5,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "NONE",
            "integrityImpact": "NONE",
            "privilegesRequired": "LOW",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
            "version": "3.1"
          },
          "exploitabilityScore": 2.8,
          "impactScore": 3.6,
          "source": "disclosure@vulncheck.com",
          "type": "Secondary"
        }
      ],
      "cvssMetricV40": [
        {
          "cvssData": {
            "Automatable": "NOT_DEFINED",
            "Recovery": "NOT_DEFINED",
            "Safety": "NOT_DEFINED",
            "attackComplexity": "LOW",
            "attackRequirements": "NONE",
            "attackVector": "NETWORK",
            "availabilityRequirement": "NOT_DEFINED",
            "baseScore": 7.1,
            "baseSeverity": "HIGH",
            "confidentialityRequirement": "NOT_DEFINED",
            "exploitMaturity": "NOT_DEFINED",
            "integrityRequirement": "NOT_DEFINED",
            "modifiedAttackComplexity": "NOT_DEFINED",
            "modifiedAttackRequirements": "NOT_DEFINED",
            "modifiedAttackVector": "NOT_DEFINED",
            "modifiedPrivilegesRequired": "NOT_DEFINED",
            "modifiedSubAvailabilityImpact": "NOT_DEFINED",
            "modifiedSubConfidentialityImpact": "NOT_DEFINED",
            "modifiedSubIntegrityImpact": "NOT_DEFINED",
            "modifiedUserInteraction": "NOT_DEFINED",
            "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
            "modifiedVulnConfidentialityImpact": "NOT_DEFINED",
            "modifiedVulnIntegrityImpact": "NOT_DEFINED",
            "privilegesRequired": "LOW",
            "providerUrgency": "NOT_DEFINED",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "NONE",
            "userInteraction": "NONE",
            "valueDensity": "NOT_DEFINED",
            "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
            "version": "4.0",
            "vulnAvailabilityImpact": "HIGH",
            "vulnConfidentialityImpact": "NONE",
            "vulnIntegrityImpact": "NONE",
            "vulnerabilityResponseEffort": "NOT_DEFINED"
          },
          "source": "disclosure@vulncheck.com",
          "type": "Secondary"
        }
      ],
      "ssvcV203": [
        {
          "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "ssvcData": {
            "id": "CVE-2026-73321",
            "options": [
              {
                "exploitation": "poc"
              },
              {
                "automatable": "no"
              },
              {
                "technicalImpact": "partial"
              }
            ],
            "role": "CISA Coordinator",
            "timestamp": "2026-09-10T13:49:59.215010Z",
            "version": "2.0.3"
          }
        }
      ]
    },
    "published": "2026-09-08T14:17:26.617",
    "references": [
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Exploit",
          "Third Party Advisory"
        ],
        "url": "https://bombobombone.github.io/posts/cve-2026-73321/"
      },
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Exploit",
          "Third Party Advisory"
        ],
        "url": "https://github.com/BomboBombone/CVE-2026-73321"
      },
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Third Party Advisory"
        ],
        "url": "https://www.vulncheck.com/advisories/xenforo-uncontrolled-recursion-dos-via-bbcode-parser"
      },
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Release Notes"
        ],
        "url": "https://xenforo.com/community/threads/security-fixes-released-for-all-xenforo-and-media-gallery-versions-2-2-0-2-3-12.239856/"
      },
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Release Notes"
        ],
        "url": "https://xenforo.com/community/threads/xenforo-2-3-13-and-add-ons-released-includes-security-fixes.239857/"
      }
    ],
    "sourceIdentifier": "disclosure@vulncheck.com",
    "vulnStatus": "Analyzed",
    "weaknesses": [
      {
        "description": [
          {
            "lang": "en",
            "value": "CWE-674"
          }
        ],
        "source": "disclosure@vulncheck.com",
        "type": "Secondary"
      }
    ]
  }
}

—

Cvss4 vector

cvss4_vector

NVD

CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

receipt

Source: NVD
Its words: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Read by: field:cve.metrics.cvssMetricV40[type=Primary].cvssData.vectorString || field:cve.metrics.cvssMetricV40[].cvssData.vectorString
Said since: 2026-10-06 12:31 UTC
Last answered: 2026-10-06 12:41 UTC
Original: open at the source

2026-10-06 12:31 UTC	CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
2026-09-29 09:45 UTC	—

What the source handed over

{
  "cve": {
    "affected": [
      {
        "affectedData": [
          {
            "defaultStatus": "unaffected",
            "product": "XenForo",
            "vendor": "XenForo",
            "versions": [
              {
                "lessThan": "2.3.13",
                "status": "affected",
                "version": "0",
                "versionType": "semver"
              }
            ]
          }
        ],
        "source": "disclosure@vulncheck.com"
      }
    ],
    "configurations": [
      {
        "nodes": [
          {
            "cpeMatch": [
              {
                "criteria": "cpe:2.3:a:xenforo:xenforo:*:*:*:*:*:*:*:*",
                "matchCriteriaId": "DD926609-EB0D-4EED-B36A-D482E4B5FDDC",
                "versionEndExcluding": "2.3.13",
                "vulnerable": true
              }
            ],
            "negate": false,
            "operator": "OR"
          }
        ]
      }
    ],
    "cveTags": [],
    "descriptions": [
      {
        "lang": "en",
        "value": "XenForo before 2.3.13 contains an uncontrolled recursion vulnerability in the BBCode parser that allows authenticated attackers to cause persistent denial of service by submitting a post with deeply nested BBCode tags. Attackers can craft a single malicious post with sufficient nesting depth to exceed PHP's stack limit, causing fatal errors that repeatedly terminate PHP-FPM workers for all visitors rendering the affected thread."
      }
    ],
    "id": "CVE-2026-73321",
    "lastModified": "2026-09-11T20:30:18.293",
    "metrics": {
      "cvssMetricV31": [
        {
          "cvssData": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 6.5,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "NONE",
            "integrityImpact": "NONE",
            "privilegesRequired": "LOW",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
            "version": "3.1"
          },
          "exploitabilityScore": 2.8,
          "impactScore": 3.6,
          "source": "disclosure@vulncheck.com",
          "type": "Secondary"
        }
      ],
      "cvssMetricV40": [
        {
          "cvssData": {
            "Automatable": "NOT_DEFINED",
            "Recovery": "NOT_DEFINED",
            "Safety": "NOT_DEFINED",
            "attackComplexity": "LOW",
            "attackRequirements": "NONE",
            "attackVector": "NETWORK",
            "availabilityRequirement": "NOT_DEFINED",
            "baseScore": 7.1,
            "baseSeverity": "HIGH",
            "confidentialityRequirement": "NOT_DEFINED",
            "exploitMaturity": "NOT_DEFINED",
            "integrityRequirement": "NOT_DEFINED",
            "modifiedAttackComplexity": "NOT_DEFINED",
            "modifiedAttackRequirements": "NOT_DEFINED",
            "modifiedAttackVector": "NOT_DEFINED",
            "modifiedPrivilegesRequired": "NOT_DEFINED",
            "modifiedSubAvailabilityImpact": "NOT_DEFINED",
            "modifiedSubConfidentialityImpact": "NOT_DEFINED",
            "modifiedSubIntegrityImpact": "NOT_DEFINED",
            "modifiedUserInteraction": "NOT_DEFINED",
            "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
            "modifiedVulnConfidentialityImpact": "NOT_DEFINED",
            "modifiedVulnIntegrityImpact": "NOT_DEFINED",
            "privilegesRequired": "LOW",
            "providerUrgency": "NOT_DEFINED",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "NONE",
            "userInteraction": "NONE",
            "valueDensity": "NOT_DEFINED",
            "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
            "version": "4.0",
            "vulnAvailabilityImpact": "HIGH",
            "vulnConfidentialityImpact": "NONE",
            "vulnIntegrityImpact": "NONE",
            "vulnerabilityResponseEffort": "NOT_DEFINED"
          },
          "source": "disclosure@vulncheck.com",
          "type": "Secondary"
        }
      ],
      "ssvcV203": [
        {
          "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "ssvcData": {
            "id": "CVE-2026-73321",
            "options": [
              {
                "exploitation": "poc"
              },
              {
                "automatable": "no"
              },
              {
                "technicalImpact": "partial"
              }
            ],
            "role": "CISA Coordinator",
            "timestamp": "2026-09-10T13:49:59.215010Z",
            "version": "2.0.3"
          }
        }
      ]
    },
    "published": "2026-09-08T14:17:26.617",
    "references": [
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Exploit",
          "Third Party Advisory"
        ],
        "url": "https://bombobombone.github.io/posts/cve-2026-73321/"
      },
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Exploit",
          "Third Party Advisory"
        ],
        "url": "https://github.com/BomboBombone/CVE-2026-73321"
      },
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Third Party Advisory"
        ],
        "url": "https://www.vulncheck.com/advisories/xenforo-uncontrolled-recursion-dos-via-bbcode-parser"
      },
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Release Notes"
        ],
        "url": "https://xenforo.com/community/threads/security-fixes-released-for-all-xenforo-and-media-gallery-versions-2-2-0-2-3-12.239856/"
      },
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Release Notes"
        ],
        "url": "https://xenforo.com/community/threads/xenforo-2-3-13-and-add-ons-released-includes-security-fixes.239857/"
      }
    ],
    "sourceIdentifier": "disclosure@vulncheck.com",
    "vulnStatus": "Analyzed",
    "weaknesses": [
      {
        "description": [
          {
            "lang": "en",
            "value": "CWE-674"
          }
        ],
        "source": "disclosure@vulncheck.com",
        "type": "Secondary"
      }
    ]
  }
}

—

CVSS vector

cvss_vector

NVD

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

receipt

Source: NVD
Its words: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Read by: field:cve.metrics.cvssMetricV31[type=Primary].cvssData.vectorString || field:cve.metrics.cvssMetricV31[].cvssData.vectorString
Said since: 2026-10-06 12:31 UTC
Last answered: 2026-10-06 12:41 UTC
Original: open at the source

2026-10-06 12:31 UTC	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
2026-09-29 09:45 UTC	—

What the source handed over

{
  "cve": {
    "affected": [
      {
        "affectedData": [
          {
            "defaultStatus": "unaffected",
            "product": "XenForo",
            "vendor": "XenForo",
            "versions": [
              {
                "lessThan": "2.3.13",
                "status": "affected",
                "version": "0",
                "versionType": "semver"
              }
            ]
          }
        ],
        "source": "disclosure@vulncheck.com"
      }
    ],
    "configurations": [
      {
        "nodes": [
          {
            "cpeMatch": [
              {
                "criteria": "cpe:2.3:a:xenforo:xenforo:*:*:*:*:*:*:*:*",
                "matchCriteriaId": "DD926609-EB0D-4EED-B36A-D482E4B5FDDC",
                "versionEndExcluding": "2.3.13",
                "vulnerable": true
              }
            ],
            "negate": false,
            "operator": "OR"
          }
        ]
      }
    ],
    "cveTags": [],
    "descriptions": [
      {
        "lang": "en",
        "value": "XenForo before 2.3.13 contains an uncontrolled recursion vulnerability in the BBCode parser that allows authenticated attackers to cause persistent denial of service by submitting a post with deeply nested BBCode tags. Attackers can craft a single malicious post with sufficient nesting depth to exceed PHP's stack limit, causing fatal errors that repeatedly terminate PHP-FPM workers for all visitors rendering the affected thread."
      }
    ],
    "id": "CVE-2026-73321",
    "lastModified": "2026-09-11T20:30:18.293",
    "metrics": {
      "cvssMetricV31": [
        {
          "cvssData": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 6.5,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "NONE",
            "integrityImpact": "NONE",
            "privilegesRequired": "LOW",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
            "version": "3.1"
          },
          "exploitabilityScore": 2.8,
          "impactScore": 3.6,
          "source": "disclosure@vulncheck.com",
          "type": "Secondary"
        }
      ],
      "cvssMetricV40": [
        {
          "cvssData": {
            "Automatable": "NOT_DEFINED",
            "Recovery": "NOT_DEFINED",
            "Safety": "NOT_DEFINED",
            "attackComplexity": "LOW",
            "attackRequirements": "NONE",
            "attackVector": "NETWORK",
            "availabilityRequirement": "NOT_DEFINED",
            "baseScore": 7.1,
            "baseSeverity": "HIGH",
            "confidentialityRequirement": "NOT_DEFINED",
            "exploitMaturity": "NOT_DEFINED",
            "integrityRequirement": "NOT_DEFINED",
            "modifiedAttackComplexity": "NOT_DEFINED",
            "modifiedAttackRequirements": "NOT_DEFINED",
            "modifiedAttackVector": "NOT_DEFINED",
            "modifiedPrivilegesRequired": "NOT_DEFINED",
            "modifiedSubAvailabilityImpact": "NOT_DEFINED",
            "modifiedSubConfidentialityImpact": "NOT_DEFINED",
            "modifiedSubIntegrityImpact": "NOT_DEFINED",
            "modifiedUserInteraction": "NOT_DEFINED",
            "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
            "modifiedVulnConfidentialityImpact": "NOT_DEFINED",
            "modifiedVulnIntegrityImpact": "NOT_DEFINED",
            "privilegesRequired": "LOW",
            "providerUrgency": "NOT_DEFINED",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "NONE",
            "userInteraction": "NONE",
            "valueDensity": "NOT_DEFINED",
            "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
            "version": "4.0",
            "vulnAvailabilityImpact": "HIGH",
            "vulnConfidentialityImpact": "NONE",
            "vulnIntegrityImpact": "NONE",
            "vulnerabilityResponseEffort": "NOT_DEFINED"
          },
          "source": "disclosure@vulncheck.com",
          "type": "Secondary"
        }
      ],
      "ssvcV203": [
        {
          "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "ssvcData": {
            "id": "CVE-2026-73321",
            "options": [
              {
                "exploitation": "poc"
              },
              {
                "automatable": "no"
              },
              {
                "technicalImpact": "partial"
              }
            ],
            "role": "CISA Coordinator",
            "timestamp": "2026-09-10T13:49:59.215010Z",
            "version": "2.0.3"
          }
        }
      ]
    },
    "published": "2026-09-08T14:17:26.617",
    "references": [
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Exploit",
          "Third Party Advisory"
        ],
        "url": "https://bombobombone.github.io/posts/cve-2026-73321/"
      },
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Exploit",
          "Third Party Advisory"
        ],
        "url": "https://github.com/BomboBombone/CVE-2026-73321"
      },
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Third Party Advisory"
        ],
        "url": "https://www.vulncheck.com/advisories/xenforo-uncontrolled-recursion-dos-via-bbcode-parser"
      },
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Release Notes"
        ],
        "url": "https://xenforo.com/community/threads/security-fixes-released-for-all-xenforo-and-media-gallery-versions-2-2-0-2-3-12.239856/"
      },
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Release Notes"
        ],
        "url": "https://xenforo.com/community/threads/xenforo-2-3-13-and-add-ons-released-includes-security-fixes.239857/"
      }
    ],
    "sourceIdentifier": "disclosure@vulncheck.com",
    "vulnStatus": "Analyzed",
    "weaknesses": [
      {
        "description": [
          {
            "lang": "en",
            "value": "CWE-674"
          }
        ],
        "source": "disclosure@vulncheck.com",
        "type": "Secondary"
      }
    ]
  }
}

—

CWE

cwe

NVD

CWE-674

receipt

Source: NVD
Its words: CWE-674
Read by: field:cve.weaknesses[].description[].value
Said since: 2026-10-06 12:31 UTC
Last answered: 2026-10-06 12:41 UTC
Original: open at the source

2026-10-06 12:31 UTC	CWE-674
2026-09-29 09:45 UTC	—

What the source handed over

{
  "cve": {
    "affected": [
      {
        "affectedData": [
          {
            "defaultStatus": "unaffected",
            "product": "XenForo",
            "vendor": "XenForo",
            "versions": [
              {
                "lessThan": "2.3.13",
                "status": "affected",
                "version": "0",
                "versionType": "semver"
              }
            ]
          }
        ],
        "source": "disclosure@vulncheck.com"
      }
    ],
    "configurations": [
      {
        "nodes": [
          {
            "cpeMatch": [
              {
                "criteria": "cpe:2.3:a:xenforo:xenforo:*:*:*:*:*:*:*:*",
                "matchCriteriaId": "DD926609-EB0D-4EED-B36A-D482E4B5FDDC",
                "versionEndExcluding": "2.3.13",
                "vulnerable": true
              }
            ],
            "negate": false,
            "operator": "OR"
          }
        ]
      }
    ],
    "cveTags": [],
    "descriptions": [
      {
        "lang": "en",
        "value": "XenForo before 2.3.13 contains an uncontrolled recursion vulnerability in the BBCode parser that allows authenticated attackers to cause persistent denial of service by submitting a post with deeply nested BBCode tags. Attackers can craft a single malicious post with sufficient nesting depth to exceed PHP's stack limit, causing fatal errors that repeatedly terminate PHP-FPM workers for all visitors rendering the affected thread."
      }
    ],
    "id": "CVE-2026-73321",
    "lastModified": "2026-09-11T20:30:18.293",
    "metrics": {
      "cvssMetricV31": [
        {
          "cvssData": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 6.5,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "NONE",
            "integrityImpact": "NONE",
            "privilegesRequired": "LOW",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
            "version": "3.1"
          },
          "exploitabilityScore": 2.8,
          "impactScore": 3.6,
          "source": "disclosure@vulncheck.com",
          "type": "Secondary"
        }
      ],
      "cvssMetricV40": [
        {
          "cvssData": {
            "Automatable": "NOT_DEFINED",
            "Recovery": "NOT_DEFINED",
            "Safety": "NOT_DEFINED",
            "attackComplexity": "LOW",
            "attackRequirements": "NONE",
            "attackVector": "NETWORK",
            "availabilityRequirement": "NOT_DEFINED",
            "baseScore": 7.1,
            "baseSeverity": "HIGH",
            "confidentialityRequirement": "NOT_DEFINED",
            "exploitMaturity": "NOT_DEFINED",
            "integrityRequirement": "NOT_DEFINED",
            "modifiedAttackComplexity": "NOT_DEFINED",
            "modifiedAttackRequirements": "NOT_DEFINED",
            "modifiedAttackVector": "NOT_DEFINED",
            "modifiedPrivilegesRequired": "NOT_DEFINED",
            "modifiedSubAvailabilityImpact": "NOT_DEFINED",
            "modifiedSubConfidentialityImpact": "NOT_DEFINED",
            "modifiedSubIntegrityImpact": "NOT_DEFINED",
            "modifiedUserInteraction": "NOT_DEFINED",
            "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
            "modifiedVulnConfidentialityImpact": "NOT_DEFINED",
            "modifiedVulnIntegrityImpact": "NOT_DEFINED",
            "privilegesRequired": "LOW",
            "providerUrgency": "NOT_DEFINED",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "NONE",
            "userInteraction": "NONE",
            "valueDensity": "NOT_DEFINED",
            "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
            "version": "4.0",
            "vulnAvailabilityImpact": "HIGH",
            "vulnConfidentialityImpact": "NONE",
            "vulnIntegrityImpact": "NONE",
            "vulnerabilityResponseEffort": "NOT_DEFINED"
          },
          "source": "disclosure@vulncheck.com",
          "type": "Secondary"
        }
      ],
      "ssvcV203": [
        {
          "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "ssvcData": {
            "id": "CVE-2026-73321",
            "options": [
              {
                "exploitation": "poc"
              },
              {
                "automatable": "no"
              },
              {
                "technicalImpact": "partial"
              }
            ],
            "role": "CISA Coordinator",
            "timestamp": "2026-09-10T13:49:59.215010Z",
            "version": "2.0.3"
          }
        }
      ]
    },
    "published": "2026-09-08T14:17:26.617",
    "references": [
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Exploit",
          "Third Party Advisory"
        ],
        "url": "https://bombobombone.github.io/posts/cve-2026-73321/"
      },
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Exploit",
          "Third Party Advisory"
        ],
        "url": "https://github.com/BomboBombone/CVE-2026-73321"
      },
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Third Party Advisory"
        ],
        "url": "https://www.vulncheck.com/advisories/xenforo-uncontrolled-recursion-dos-via-bbcode-parser"
      },
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Release Notes"
        ],
        "url": "https://xenforo.com/community/threads/security-fixes-released-for-all-xenforo-and-media-gallery-versions-2-2-0-2-3-12.239856/"
      },
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Release Notes"
        ],
        "url": "https://xenforo.com/community/threads/xenforo-2-3-13-and-add-ons-released-includes-security-fixes.239857/"
      }
    ],
    "sourceIdentifier": "disclosure@vulncheck.com",
    "vulnStatus": "Analyzed",
    "weaknesses": [
      {
        "description": [
          {
            "lang": "en",
            "value": "CWE-674"
          }
        ],
        "source": "disclosure@vulncheck.com",
        "type": "Secondary"
      }
    ]
  }
}

—

Exploitation

exploitation

NVD

poc

A public proof of concept exists, or exploitation is trivial.

receipt

Source: NVD
Its words: poc
Read by: field:cve.metrics.ssvcV203[].ssvcData.options[].exploitation
Said since: 2026-10-06 12:31 UTC
Last answered: 2026-10-06 12:41 UTC
Original: open at the source

2026-10-06 12:31 UTC	poc
2026-09-29 09:45 UTC	—

What the source handed over

{
  "cve": {
    "affected": [
      {
        "affectedData": [
          {
            "defaultStatus": "unaffected",
            "product": "XenForo",
            "vendor": "XenForo",
            "versions": [
              {
                "lessThan": "2.3.13",
                "status": "affected",
                "version": "0",
                "versionType": "semver"
              }
            ]
          }
        ],
        "source": "disclosure@vulncheck.com"
      }
    ],
    "configurations": [
      {
        "nodes": [
          {
            "cpeMatch": [
              {
                "criteria": "cpe:2.3:a:xenforo:xenforo:*:*:*:*:*:*:*:*",
                "matchCriteriaId": "DD926609-EB0D-4EED-B36A-D482E4B5FDDC",
                "versionEndExcluding": "2.3.13",
                "vulnerable": true
              }
            ],
            "negate": false,
            "operator": "OR"
          }
        ]
      }
    ],
    "cveTags": [],
    "descriptions": [
      {
        "lang": "en",
        "value": "XenForo before 2.3.13 contains an uncontrolled recursion vulnerability in the BBCode parser that allows authenticated attackers to cause persistent denial of service by submitting a post with deeply nested BBCode tags. Attackers can craft a single malicious post with sufficient nesting depth to exceed PHP's stack limit, causing fatal errors that repeatedly terminate PHP-FPM workers for all visitors rendering the affected thread."
      }
    ],
    "id": "CVE-2026-73321",
    "lastModified": "2026-09-11T20:30:18.293",
    "metrics": {
      "cvssMetricV31": [
        {
          "cvssData": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 6.5,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "NONE",
            "integrityImpact": "NONE",
            "privilegesRequired": "LOW",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
            "version": "3.1"
          },
          "exploitabilityScore": 2.8,
          "impactScore": 3.6,
          "source": "disclosure@vulncheck.com",
          "type": "Secondary"
        }
      ],
      "cvssMetricV40": [
        {
          "cvssData": {
            "Automatable": "NOT_DEFINED",
            "Recovery": "NOT_DEFINED",
            "Safety": "NOT_DEFINED",
            "attackComplexity": "LOW",
            "attackRequirements": "NONE",
            "attackVector": "NETWORK",
            "availabilityRequirement": "NOT_DEFINED",
            "baseScore": 7.1,
            "baseSeverity": "HIGH",
            "confidentialityRequirement": "NOT_DEFINED",
            "exploitMaturity": "NOT_DEFINED",
            "integrityRequirement": "NOT_DEFINED",
            "modifiedAttackComplexity": "NOT_DEFINED",
            "modifiedAttackRequirements": "NOT_DEFINED",
            "modifiedAttackVector": "NOT_DEFINED",
            "modifiedPrivilegesRequired": "NOT_DEFINED",
            "modifiedSubAvailabilityImpact": "NOT_DEFINED",
            "modifiedSubConfidentialityImpact": "NOT_DEFINED",
            "modifiedSubIntegrityImpact": "NOT_DEFINED",
            "modifiedUserInteraction": "NOT_DEFINED",
            "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
            "modifiedVulnConfidentialityImpact": "NOT_DEFINED",
            "modifiedVulnIntegrityImpact": "NOT_DEFINED",
            "privilegesRequired": "LOW",
            "providerUrgency": "NOT_DEFINED",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "NONE",
            "userInteraction": "NONE",
            "valueDensity": "NOT_DEFINED",
            "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
            "version": "4.0",
            "vulnAvailabilityImpact": "HIGH",
            "vulnConfidentialityImpact": "NONE",
            "vulnIntegrityImpact": "NONE",
            "vulnerabilityResponseEffort": "NOT_DEFINED"
          },
          "source": "disclosure@vulncheck.com",
          "type": "Secondary"
        }
      ],
      "ssvcV203": [
        {
          "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "ssvcData": {
            "id": "CVE-2026-73321",
            "options": [
              {
                "exploitation": "poc"
              },
              {
                "automatable": "no"
              },
              {
                "technicalImpact": "partial"
              }
            ],
            "role": "CISA Coordinator",
            "timestamp": "2026-09-10T13:49:59.215010Z",
            "version": "2.0.3"
          }
        }
      ]
    },
    "published": "2026-09-08T14:17:26.617",
    "references": [
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Exploit",
          "Third Party Advisory"
        ],
        "url": "https://bombobombone.github.io/posts/cve-2026-73321/"
      },
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Exploit",
          "Third Party Advisory"
        ],
        "url": "https://github.com/BomboBombone/CVE-2026-73321"
      },
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Third Party Advisory"
        ],
        "url": "https://www.vulncheck.com/advisories/xenforo-uncontrolled-recursion-dos-via-bbcode-parser"
      },
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Release Notes"
        ],
        "url": "https://xenforo.com/community/threads/security-fixes-released-for-all-xenforo-and-media-gallery-versions-2-2-0-2-3-12.239856/"
      },
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Release Notes"
        ],
        "url": "https://xenforo.com/community/threads/xenforo-2-3-13-and-add-ons-released-includes-security-fixes.239857/"
      }
    ],
    "sourceIdentifier": "disclosure@vulncheck.com",
    "vulnStatus": "Analyzed",
    "weaknesses": [
      {
        "description": [
          {
            "lang": "en",
            "value": "CWE-674"
          }
        ],
        "source": "disclosure@vulncheck.com",
        "type": "Secondary"
      }
    ]
  }
}

—

Fixed in

fixed_in

NVD

2.3.13

receipt

Source: NVD
Its words: 2.3.13
Read by: field:cve.affected[].affectedData[].versions[status=affected].lessThan
Said since: 2026-10-06 12:31 UTC
Last answered: 2026-10-06 12:41 UTC
Original: open at the source

2026-10-06 12:31 UTC	2.3.13
2026-09-29 09:45 UTC	—

What the source handed over

{
  "cve": {
    "affected": [
      {
        "affectedData": [
          {
            "defaultStatus": "unaffected",
            "product": "XenForo",
            "vendor": "XenForo",
            "versions": [
              {
                "lessThan": "2.3.13",
                "status": "affected",
                "version": "0",
                "versionType": "semver"
              }
            ]
          }
        ],
        "source": "disclosure@vulncheck.com"
      }
    ],
    "configurations": [
      {
        "nodes": [
          {
            "cpeMatch": [
              {
                "criteria": "cpe:2.3:a:xenforo:xenforo:*:*:*:*:*:*:*:*",
                "matchCriteriaId": "DD926609-EB0D-4EED-B36A-D482E4B5FDDC",
                "versionEndExcluding": "2.3.13",
                "vulnerable": true
              }
            ],
            "negate": false,
            "operator": "OR"
          }
        ]
      }
    ],
    "cveTags": [],
    "descriptions": [
      {
        "lang": "en",
        "value": "XenForo before 2.3.13 contains an uncontrolled recursion vulnerability in the BBCode parser that allows authenticated attackers to cause persistent denial of service by submitting a post with deeply nested BBCode tags. Attackers can craft a single malicious post with sufficient nesting depth to exceed PHP's stack limit, causing fatal errors that repeatedly terminate PHP-FPM workers for all visitors rendering the affected thread."
      }
    ],
    "id": "CVE-2026-73321",
    "lastModified": "2026-09-11T20:30:18.293",
    "metrics": {
      "cvssMetricV31": [
        {
          "cvssData": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 6.5,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "NONE",
            "integrityImpact": "NONE",
            "privilegesRequired": "LOW",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
            "version": "3.1"
          },
          "exploitabilityScore": 2.8,
          "impactScore": 3.6,
          "source": "disclosure@vulncheck.com",
          "type": "Secondary"
        }
      ],
      "cvssMetricV40": [
        {
          "cvssData": {
            "Automatable": "NOT_DEFINED",
            "Recovery": "NOT_DEFINED",
            "Safety": "NOT_DEFINED",
            "attackComplexity": "LOW",
            "attackRequirements": "NONE",
            "attackVector": "NETWORK",
            "availabilityRequirement": "NOT_DEFINED",
            "baseScore": 7.1,
            "baseSeverity": "HIGH",
            "confidentialityRequirement": "NOT_DEFINED",
            "exploitMaturity": "NOT_DEFINED",
            "integrityRequirement": "NOT_DEFINED",
            "modifiedAttackComplexity": "NOT_DEFINED",
            "modifiedAttackRequirements": "NOT_DEFINED",
            "modifiedAttackVector": "NOT_DEFINED",
            "modifiedPrivilegesRequired": "NOT_DEFINED",
            "modifiedSubAvailabilityImpact": "NOT_DEFINED",
            "modifiedSubConfidentialityImpact": "NOT_DEFINED",
            "modifiedSubIntegrityImpact": "NOT_DEFINED",
            "modifiedUserInteraction": "NOT_DEFINED",
            "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
            "modifiedVulnConfidentialityImpact": "NOT_DEFINED",
            "modifiedVulnIntegrityImpact": "NOT_DEFINED",
            "privilegesRequired": "LOW",
            "providerUrgency": "NOT_DEFINED",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "NONE",
            "userInteraction": "NONE",
            "valueDensity": "NOT_DEFINED",
            "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
            "version": "4.0",
            "vulnAvailabilityImpact": "HIGH",
            "vulnConfidentialityImpact": "NONE",
            "vulnIntegrityImpact": "NONE",
            "vulnerabilityResponseEffort": "NOT_DEFINED"
          },
          "source": "disclosure@vulncheck.com",
          "type": "Secondary"
        }
      ],
      "ssvcV203": [
        {
          "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "ssvcData": {
            "id": "CVE-2026-73321",
            "options": [
              {
                "exploitation": "poc"
              },
              {
                "automatable": "no"
              },
              {
                "technicalImpact": "partial"
              }
            ],
            "role": "CISA Coordinator",
            "timestamp": "2026-09-10T13:49:59.215010Z",
            "version": "2.0.3"
          }
        }
      ]
    },
    "published": "2026-09-08T14:17:26.617",
    "references": [
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Exploit",
          "Third Party Advisory"
        ],
        "url": "https://bombobombone.github.io/posts/cve-2026-73321/"
      },
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Exploit",
          "Third Party Advisory"
        ],
        "url": "https://github.com/BomboBombone/CVE-2026-73321"
      },
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Third Party Advisory"
        ],
        "url": "https://www.vulncheck.com/advisories/xenforo-uncontrolled-recursion-dos-via-bbcode-parser"
      },
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Release Notes"
        ],
        "url": "https://xenforo.com/community/threads/security-fixes-released-for-all-xenforo-and-media-gallery-versions-2-2-0-2-3-12.239856/"
      },
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Release Notes"
        ],
        "url": "https://xenforo.com/community/threads/xenforo-2-3-13-and-add-ons-released-includes-security-fixes.239857/"
      }
    ],
    "sourceIdentifier": "disclosure@vulncheck.com",
    "vulnStatus": "Analyzed",
    "weaknesses": [
      {
        "description": [
          {
            "lang": "en",
            "value": "CWE-674"
          }
        ],
        "source": "disclosure@vulncheck.com",
        "type": "Secondary"
      }
    ]
  }
}

—

Product

product

NVD

XenForo

receipt

Source: NVD
Its words: XenForo
Read by: field:cve.affected[].affectedData[].product
Said since: 2026-09-29 17:49 UTC
Last answered: 2026-10-06 12:41 UTC
Original: open at the source

2026-09-29 17:49 UTC	XenForo
2026-09-29 09:45 UTC	—

What the source handed over

{
  "cve": {
    "affected": [
      {
        "affectedData": [
          {
            "defaultStatus": "unaffected",
            "product": "XenForo",
            "vendor": "XenForo",
            "versions": [
              {
                "lessThan": "2.3.13",
                "status": "affected",
                "version": "0",
                "versionType": "semver"
              }
            ]
          }
        ],
        "source": "disclosure@vulncheck.com"
      }
    ],
    "configurations": [
      {
        "nodes": [
          {
            "cpeMatch": [
              {
                "criteria": "cpe:2.3:a:xenforo:xenforo:*:*:*:*:*:*:*:*",
                "matchCriteriaId": "DD926609-EB0D-4EED-B36A-D482E4B5FDDC",
                "versionEndExcluding": "2.3.13",
                "vulnerable": true
              }
            ],
            "negate": false,
            "operator": "OR"
          }
        ]
      }
    ],
    "cveTags": [],
    "descriptions": [
      {
        "lang": "en",
        "value": "XenForo before 2.3.13 contains an uncontrolled recursion vulnerability in the BBCode parser that allows authenticated attackers to cause persistent denial of service by submitting a post with deeply nested BBCode tags. Attackers can craft a single malicious post with sufficient nesting depth to exceed PHP's stack limit, causing fatal errors that repeatedly terminate PHP-FPM workers for all visitors rendering the affected thread."
      }
    ],
    "id": "CVE-2026-73321",
    "lastModified": "2026-09-11T20:30:18.293",
    "metrics": {
      "cvssMetricV31": [
        {
          "cvssData": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 6.5,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "NONE",
            "integrityImpact": "NONE",
            "privilegesRequired": "LOW",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
            "version": "3.1"
          },
          "exploitabilityScore": 2.8,
          "impactScore": 3.6,
          "source": "disclosure@vulncheck.com",
          "type": "Secondary"
        }
      ],
      "cvssMetricV40": [
        {
          "cvssData": {
            "Automatable": "NOT_DEFINED",
            "Recovery": "NOT_DEFINED",
            "Safety": "NOT_DEFINED",
            "attackComplexity": "LOW",
            "attackRequirements": "NONE",
            "attackVector": "NETWORK",
            "availabilityRequirement": "NOT_DEFINED",
            "baseScore": 7.1,
            "baseSeverity": "HIGH",
            "confidentialityRequirement": "NOT_DEFINED",
            "exploitMaturity": "NOT_DEFINED",
            "integrityRequirement": "NOT_DEFINED",
            "modifiedAttackComplexity": "NOT_DEFINED",
            "modifiedAttackRequirements": "NOT_DEFINED",
            "modifiedAttackVector": "NOT_DEFINED",
            "modifiedPrivilegesRequired": "NOT_DEFINED",
            "modifiedSubAvailabilityImpact": "NOT_DEFINED",
            "modifiedSubConfidentialityImpact": "NOT_DEFINED",
            "modifiedSubIntegrityImpact": "NOT_DEFINED",
            "modifiedUserInteraction": "NOT_DEFINED",
            "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
            "modifiedVulnConfidentialityImpact": "NOT_DEFINED",
            "modifiedVulnIntegrityImpact": "NOT_DEFINED",
            "privilegesRequired": "LOW",
            "providerUrgency": "NOT_DEFINED",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "NONE",
            "userInteraction": "NONE",
            "valueDensity": "NOT_DEFINED",
            "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
            "version": "4.0",
            "vulnAvailabilityImpact": "HIGH",
            "vulnConfidentialityImpact": "NONE",
            "vulnIntegrityImpact": "NONE",
            "vulnerabilityResponseEffort": "NOT_DEFINED"
          },
          "source": "disclosure@vulncheck.com",
          "type": "Secondary"
        }
      ],
      "ssvcV203": [
        {
          "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "ssvcData": {
            "id": "CVE-2026-73321",
            "options": [
              {
                "exploitation": "poc"
              },
              {
                "automatable": "no"
              },
              {
                "technicalImpact": "partial"
              }
            ],
            "role": "CISA Coordinator",
            "timestamp": "2026-09-10T13:49:59.215010Z",
            "version": "2.0.3"
          }
        }
      ]
    },
    "published": "2026-09-08T14:17:26.617",
    "references": [
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Exploit",
          "Third Party Advisory"
        ],
        "url": "https://bombobombone.github.io/posts/cve-2026-73321/"
      },
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Exploit",
          "Third Party Advisory"
        ],
        "url": "https://github.com/BomboBombone/CVE-2026-73321"
      },
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Third Party Advisory"
        ],
        "url": "https://www.vulncheck.com/advisories/xenforo-uncontrolled-recursion-dos-via-bbcode-parser"
      },
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Release Notes"
        ],
        "url": "https://xenforo.com/community/threads/security-fixes-released-for-all-xenforo-and-media-gallery-versions-2-2-0-2-3-12.239856/"
      },
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Release Notes"
        ],
        "url": "https://xenforo.com/community/threads/xenforo-2-3-13-and-add-ons-released-includes-security-fixes.239857/"
      }
    ],
    "sourceIdentifier": "disclosure@vulncheck.com",
    "vulnStatus": "Analyzed",
    "weaknesses": [
      {
        "description": [
          {
            "lang": "en",
            "value": "CWE-674"
          }
        ],
        "source": "disclosure@vulncheck.com",
        "type": "Secondary"
      }
    ]
  }
}

—

Severity

severity

NVD

MEDIUM

From 4.0 to 6.9.

receipt

Source: NVD
Its words: MEDIUM
Read by: field:cve.metrics.cvssMetricV31[type=Primary].cvssData.baseSeverity || field:cve.metrics.cvssMetricV31[].cvssData.baseSeverity
Said since: 2026-10-06 12:31 UTC
Last answered: 2026-10-06 12:41 UTC
Original: open at the source

2026-10-06 12:31 UTC	MEDIUM
2026-09-29 09:45 UTC	—

What the source handed over

{
  "cve": {
    "affected": [
      {
        "affectedData": [
          {
            "defaultStatus": "unaffected",
            "product": "XenForo",
            "vendor": "XenForo",
            "versions": [
              {
                "lessThan": "2.3.13",
                "status": "affected",
                "version": "0",
                "versionType": "semver"
              }
            ]
          }
        ],
        "source": "disclosure@vulncheck.com"
      }
    ],
    "configurations": [
      {
        "nodes": [
          {
            "cpeMatch": [
              {
                "criteria": "cpe:2.3:a:xenforo:xenforo:*:*:*:*:*:*:*:*",
                "matchCriteriaId": "DD926609-EB0D-4EED-B36A-D482E4B5FDDC",
                "versionEndExcluding": "2.3.13",
                "vulnerable": true
              }
            ],
            "negate": false,
            "operator": "OR"
          }
        ]
      }
    ],
    "cveTags": [],
    "descriptions": [
      {
        "lang": "en",
        "value": "XenForo before 2.3.13 contains an uncontrolled recursion vulnerability in the BBCode parser that allows authenticated attackers to cause persistent denial of service by submitting a post with deeply nested BBCode tags. Attackers can craft a single malicious post with sufficient nesting depth to exceed PHP's stack limit, causing fatal errors that repeatedly terminate PHP-FPM workers for all visitors rendering the affected thread."
      }
    ],
    "id": "CVE-2026-73321",
    "lastModified": "2026-09-11T20:30:18.293",
    "metrics": {
      "cvssMetricV31": [
        {
          "cvssData": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 6.5,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "NONE",
            "integrityImpact": "NONE",
            "privilegesRequired": "LOW",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
            "version": "3.1"
          },
          "exploitabilityScore": 2.8,
          "impactScore": 3.6,
          "source": "disclosure@vulncheck.com",
          "type": "Secondary"
        }
      ],
      "cvssMetricV40": [
        {
          "cvssData": {
            "Automatable": "NOT_DEFINED",
            "Recovery": "NOT_DEFINED",
            "Safety": "NOT_DEFINED",
            "attackComplexity": "LOW",
            "attackRequirements": "NONE",
            "attackVector": "NETWORK",
            "availabilityRequirement": "NOT_DEFINED",
            "baseScore": 7.1,
            "baseSeverity": "HIGH",
            "confidentialityRequirement": "NOT_DEFINED",
            "exploitMaturity": "NOT_DEFINED",
            "integrityRequirement": "NOT_DEFINED",
            "modifiedAttackComplexity": "NOT_DEFINED",
            "modifiedAttackRequirements": "NOT_DEFINED",
            "modifiedAttackVector": "NOT_DEFINED",
            "modifiedPrivilegesRequired": "NOT_DEFINED",
            "modifiedSubAvailabilityImpact": "NOT_DEFINED",
            "modifiedSubConfidentialityImpact": "NOT_DEFINED",
            "modifiedSubIntegrityImpact": "NOT_DEFINED",
            "modifiedUserInteraction": "NOT_DEFINED",
            "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
            "modifiedVulnConfidentialityImpact": "NOT_DEFINED",
            "modifiedVulnIntegrityImpact": "NOT_DEFINED",
            "privilegesRequired": "LOW",
            "providerUrgency": "NOT_DEFINED",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "NONE",
            "userInteraction": "NONE",
            "valueDensity": "NOT_DEFINED",
            "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
            "version": "4.0",
            "vulnAvailabilityImpact": "HIGH",
            "vulnConfidentialityImpact": "NONE",
            "vulnIntegrityImpact": "NONE",
            "vulnerabilityResponseEffort": "NOT_DEFINED"
          },
          "source": "disclosure@vulncheck.com",
          "type": "Secondary"
        }
      ],
      "ssvcV203": [
        {
          "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "ssvcData": {
            "id": "CVE-2026-73321",
            "options": [
              {
                "exploitation": "poc"
              },
              {
                "automatable": "no"
              },
              {
                "technicalImpact": "partial"
              }
            ],
            "role": "CISA Coordinator",
            "timestamp": "2026-09-10T13:49:59.215010Z",
            "version": "2.0.3"
          }
        }
      ]
    },
    "published": "2026-09-08T14:17:26.617",
    "references": [
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Exploit",
          "Third Party Advisory"
        ],
        "url": "https://bombobombone.github.io/posts/cve-2026-73321/"
      },
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Exploit",
          "Third Party Advisory"
        ],
        "url": "https://github.com/BomboBombone/CVE-2026-73321"
      },
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Third Party Advisory"
        ],
        "url": "https://www.vulncheck.com/advisories/xenforo-uncontrolled-recursion-dos-via-bbcode-parser"
      },
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Release Notes"
        ],
        "url": "https://xenforo.com/community/threads/security-fixes-released-for-all-xenforo-and-media-gallery-versions-2-2-0-2-3-12.239856/"
      },
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Release Notes"
        ],
        "url": "https://xenforo.com/community/threads/xenforo-2-3-13-and-add-ons-released-includes-security-fixes.239857/"
      }
    ],
    "sourceIdentifier": "disclosure@vulncheck.com",
    "vulnStatus": "Analyzed",
    "weaknesses": [
      {
        "description": [
          {
            "lang": "en",
            "value": "CWE-674"
          }
        ],
        "source": "disclosure@vulncheck.com",
        "type": "Secondary"
      }
    ]
  }
}

medium

Status

status

NVD

Analyzed

receipt

Source: NVD
Its words: Analyzed
Read by: field:cve.vulnStatus
Said since: 2026-09-29 09:45 UTC
Last answered: 2026-10-06 12:41 UTC
Original: open at the source

What the source handed over

{
  "cve": {
    "affected": [
      {
        "affectedData": [
          {
            "defaultStatus": "unaffected",
            "product": "XenForo",
            "vendor": "XenForo",
            "versions": [
              {
                "lessThan": "2.3.13",
                "status": "affected",
                "version": "0",
                "versionType": "semver"
              }
            ]
          }
        ],
        "source": "disclosure@vulncheck.com"
      }
    ],
    "configurations": [
      {
        "nodes": [
          {
            "cpeMatch": [
              {
                "criteria": "cpe:2.3:a:xenforo:xenforo:*:*:*:*:*:*:*:*",
                "matchCriteriaId": "DD926609-EB0D-4EED-B36A-D482E4B5FDDC",
                "versionEndExcluding": "2.3.13",
                "vulnerable": true
              }
            ],
            "negate": false,
            "operator": "OR"
          }
        ]
      }
    ],
    "cveTags": [],
    "descriptions": [
      {
        "lang": "en",
        "value": "XenForo before 2.3.13 contains an uncontrolled recursion vulnerability in the BBCode parser that allows authenticated attackers to cause persistent denial of service by submitting a post with deeply nested BBCode tags. Attackers can craft a single malicious post with sufficient nesting depth to exceed PHP's stack limit, causing fatal errors that repeatedly terminate PHP-FPM workers for all visitors rendering the affected thread."
      }
    ],
    "id": "CVE-2026-73321",
    "lastModified": "2026-09-11T20:30:18.293",
    "metrics": {
      "cvssMetricV31": [
        {
          "cvssData": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 6.5,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "NONE",
            "integrityImpact": "NONE",
            "privilegesRequired": "LOW",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
            "version": "3.1"
          },
          "exploitabilityScore": 2.8,
          "impactScore": 3.6,
          "source": "disclosure@vulncheck.com",
          "type": "Secondary"
        }
      ],
      "cvssMetricV40": [
        {
          "cvssData": {
            "Automatable": "NOT_DEFINED",
            "Recovery": "NOT_DEFINED",
            "Safety": "NOT_DEFINED",
            "attackComplexity": "LOW",
            "attackRequirements": "NONE",
            "attackVector": "NETWORK",
            "availabilityRequirement": "NOT_DEFINED",
            "baseScore": 7.1,
            "baseSeverity": "HIGH",
            "confidentialityRequirement": "NOT_DEFINED",
            "exploitMaturity": "NOT_DEFINED",
            "integrityRequirement": "NOT_DEFINED",
            "modifiedAttackComplexity": "NOT_DEFINED",
            "modifiedAttackRequirements": "NOT_DEFINED",
            "modifiedAttackVector": "NOT_DEFINED",
            "modifiedPrivilegesRequired": "NOT_DEFINED",
            "modifiedSubAvailabilityImpact": "NOT_DEFINED",
            "modifiedSubConfidentialityImpact": "NOT_DEFINED",
            "modifiedSubIntegrityImpact": "NOT_DEFINED",
            "modifiedUserInteraction": "NOT_DEFINED",
            "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
            "modifiedVulnConfidentialityImpact": "NOT_DEFINED",
            "modifiedVulnIntegrityImpact": "NOT_DEFINED",
            "privilegesRequired": "LOW",
            "providerUrgency": "NOT_DEFINED",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "NONE",
            "userInteraction": "NONE",
            "valueDensity": "NOT_DEFINED",
            "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
            "version": "4.0",
            "vulnAvailabilityImpact": "HIGH",
            "vulnConfidentialityImpact": "NONE",
            "vulnIntegrityImpact": "NONE",
            "vulnerabilityResponseEffort": "NOT_DEFINED"
          },
          "source": "disclosure@vulncheck.com",
          "type": "Secondary"
        }
      ],
      "ssvcV203": [
        {
          "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "ssvcData": {
            "id": "CVE-2026-73321",
            "options": [
              {
                "exploitation": "poc"
              },
              {
                "automatable": "no"
              },
              {
                "technicalImpact": "partial"
              }
            ],
            "role": "CISA Coordinator",
            "timestamp": "2026-09-10T13:49:59.215010Z",
            "version": "2.0.3"
          }
        }
      ]
    },
    "published": "2026-09-08T14:17:26.617",
    "references": [
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Exploit",
          "Third Party Advisory"
        ],
        "url": "https://bombobombone.github.io/posts/cve-2026-73321/"
      },
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Exploit",
          "Third Party Advisory"
        ],
        "url": "https://github.com/BomboBombone/CVE-2026-73321"
      },
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Third Party Advisory"
        ],
        "url": "https://www.vulncheck.com/advisories/xenforo-uncontrolled-recursion-dos-via-bbcode-parser"
      },
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Release Notes"
        ],
        "url": "https://xenforo.com/community/threads/security-fixes-released-for-all-xenforo-and-media-gallery-versions-2-2-0-2-3-12.239856/"
      },
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Release Notes"
        ],
        "url": "https://xenforo.com/community/threads/xenforo-2-3-13-and-add-ons-released-includes-security-fixes.239857/"
      }
    ],
    "sourceIdentifier": "disclosure@vulncheck.com",
    "vulnStatus": "Analyzed",
    "weaknesses": [
      {
        "description": [
          {
            "lang": "en",
            "value": "CWE-674"
          }
        ],
        "source": "disclosure@vulncheck.com",
        "type": "Secondary"
      }
    ]
  }
}

—

Technical impact

technical_impact

NVD

partial

The attacker gains limited control, or limited information.

receipt

Source: NVD
Its words: partial
Read by: field:cve.metrics.ssvcV203[].ssvcData.options[].technicalImpact
Said since: 2026-10-06 12:31 UTC
Last answered: 2026-10-06 12:41 UTC
Original: open at the source

2026-10-06 12:31 UTC	partial
2026-09-29 09:45 UTC	—

What the source handed over

{
  "cve": {
    "affected": [
      {
        "affectedData": [
          {
            "defaultStatus": "unaffected",
            "product": "XenForo",
            "vendor": "XenForo",
            "versions": [
              {
                "lessThan": "2.3.13",
                "status": "affected",
                "version": "0",
                "versionType": "semver"
              }
            ]
          }
        ],
        "source": "disclosure@vulncheck.com"
      }
    ],
    "configurations": [
      {
        "nodes": [
          {
            "cpeMatch": [
              {
                "criteria": "cpe:2.3:a:xenforo:xenforo:*:*:*:*:*:*:*:*",
                "matchCriteriaId": "DD926609-EB0D-4EED-B36A-D482E4B5FDDC",
                "versionEndExcluding": "2.3.13",
                "vulnerable": true
              }
            ],
            "negate": false,
            "operator": "OR"
          }
        ]
      }
    ],
    "cveTags": [],
    "descriptions": [
      {
        "lang": "en",
        "value": "XenForo before 2.3.13 contains an uncontrolled recursion vulnerability in the BBCode parser that allows authenticated attackers to cause persistent denial of service by submitting a post with deeply nested BBCode tags. Attackers can craft a single malicious post with sufficient nesting depth to exceed PHP's stack limit, causing fatal errors that repeatedly terminate PHP-FPM workers for all visitors rendering the affected thread."
      }
    ],
    "id": "CVE-2026-73321",
    "lastModified": "2026-09-11T20:30:18.293",
    "metrics": {
      "cvssMetricV31": [
        {
          "cvssData": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 6.5,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "NONE",
            "integrityImpact": "NONE",
            "privilegesRequired": "LOW",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
            "version": "3.1"
          },
          "exploitabilityScore": 2.8,
          "impactScore": 3.6,
          "source": "disclosure@vulncheck.com",
          "type": "Secondary"
        }
      ],
      "cvssMetricV40": [
        {
          "cvssData": {
            "Automatable": "NOT_DEFINED",
            "Recovery": "NOT_DEFINED",
            "Safety": "NOT_DEFINED",
            "attackComplexity": "LOW",
            "attackRequirements": "NONE",
            "attackVector": "NETWORK",
            "availabilityRequirement": "NOT_DEFINED",
            "baseScore": 7.1,
            "baseSeverity": "HIGH",
            "confidentialityRequirement": "NOT_DEFINED",
            "exploitMaturity": "NOT_DEFINED",
            "integrityRequirement": "NOT_DEFINED",
            "modifiedAttackComplexity": "NOT_DEFINED",
            "modifiedAttackRequirements": "NOT_DEFINED",
            "modifiedAttackVector": "NOT_DEFINED",
            "modifiedPrivilegesRequired": "NOT_DEFINED",
            "modifiedSubAvailabilityImpact": "NOT_DEFINED",
            "modifiedSubConfidentialityImpact": "NOT_DEFINED",
            "modifiedSubIntegrityImpact": "NOT_DEFINED",
            "modifiedUserInteraction": "NOT_DEFINED",
            "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
            "modifiedVulnConfidentialityImpact": "NOT_DEFINED",
            "modifiedVulnIntegrityImpact": "NOT_DEFINED",
            "privilegesRequired": "LOW",
            "providerUrgency": "NOT_DEFINED",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "NONE",
            "userInteraction": "NONE",
            "valueDensity": "NOT_DEFINED",
            "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
            "version": "4.0",
            "vulnAvailabilityImpact": "HIGH",
            "vulnConfidentialityImpact": "NONE",
            "vulnIntegrityImpact": "NONE",
            "vulnerabilityResponseEffort": "NOT_DEFINED"
          },
          "source": "disclosure@vulncheck.com",
          "type": "Secondary"
        }
      ],
      "ssvcV203": [
        {
          "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "ssvcData": {
            "id": "CVE-2026-73321",
            "options": [
              {
                "exploitation": "poc"
              },
              {
                "automatable": "no"
              },
              {
                "technicalImpact": "partial"
              }
            ],
            "role": "CISA Coordinator",
            "timestamp": "2026-09-10T13:49:59.215010Z",
            "version": "2.0.3"
          }
        }
      ]
    },
    "published": "2026-09-08T14:17:26.617",
    "references": [
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Exploit",
          "Third Party Advisory"
        ],
        "url": "https://bombobombone.github.io/posts/cve-2026-73321/"
      },
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Exploit",
          "Third Party Advisory"
        ],
        "url": "https://github.com/BomboBombone/CVE-2026-73321"
      },
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Third Party Advisory"
        ],
        "url": "https://www.vulncheck.com/advisories/xenforo-uncontrolled-recursion-dos-via-bbcode-parser"
      },
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Release Notes"
        ],
        "url": "https://xenforo.com/community/threads/security-fixes-released-for-all-xenforo-and-media-gallery-versions-2-2-0-2-3-12.239856/"
      },
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Release Notes"
        ],
        "url": "https://xenforo.com/community/threads/xenforo-2-3-13-and-add-ons-released-includes-security-fixes.239857/"
      }
    ],
    "sourceIdentifier": "disclosure@vulncheck.com",
    "vulnStatus": "Analyzed",
    "weaknesses": [
      {
        "description": [
          {
            "lang": "en",
            "value": "CWE-674"
          }
        ],
        "source": "disclosure@vulncheck.com",
        "type": "Secondary"
      }
    ]
  }
}

—

Vendor

vendor

NVD

XenForo

receipt

Source: NVD
Its words: XenForo
Read by: field:cve.affected[].affectedData[].vendor
Said since: 2026-09-29 17:49 UTC
Last answered: 2026-10-06 12:41 UTC
Original: open at the source

2026-09-29 17:49 UTC	XenForo
2026-09-29 09:45 UTC	—

What the source handed over

{
  "cve": {
    "affected": [
      {
        "affectedData": [
          {
            "defaultStatus": "unaffected",
            "product": "XenForo",
            "vendor": "XenForo",
            "versions": [
              {
                "lessThan": "2.3.13",
                "status": "affected",
                "version": "0",
                "versionType": "semver"
              }
            ]
          }
        ],
        "source": "disclosure@vulncheck.com"
      }
    ],
    "configurations": [
      {
        "nodes": [
          {
            "cpeMatch": [
              {
                "criteria": "cpe:2.3:a:xenforo:xenforo:*:*:*:*:*:*:*:*",
                "matchCriteriaId": "DD926609-EB0D-4EED-B36A-D482E4B5FDDC",
                "versionEndExcluding": "2.3.13",
                "vulnerable": true
              }
            ],
            "negate": false,
            "operator": "OR"
          }
        ]
      }
    ],
    "cveTags": [],
    "descriptions": [
      {
        "lang": "en",
        "value": "XenForo before 2.3.13 contains an uncontrolled recursion vulnerability in the BBCode parser that allows authenticated attackers to cause persistent denial of service by submitting a post with deeply nested BBCode tags. Attackers can craft a single malicious post with sufficient nesting depth to exceed PHP's stack limit, causing fatal errors that repeatedly terminate PHP-FPM workers for all visitors rendering the affected thread."
      }
    ],
    "id": "CVE-2026-73321",
    "lastModified": "2026-09-11T20:30:18.293",
    "metrics": {
      "cvssMetricV31": [
        {
          "cvssData": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 6.5,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "NONE",
            "integrityImpact": "NONE",
            "privilegesRequired": "LOW",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
            "version": "3.1"
          },
          "exploitabilityScore": 2.8,
          "impactScore": 3.6,
          "source": "disclosure@vulncheck.com",
          "type": "Secondary"
        }
      ],
      "cvssMetricV40": [
        {
          "cvssData": {
            "Automatable": "NOT_DEFINED",
            "Recovery": "NOT_DEFINED",
            "Safety": "NOT_DEFINED",
            "attackComplexity": "LOW",
            "attackRequirements": "NONE",
            "attackVector": "NETWORK",
            "availabilityRequirement": "NOT_DEFINED",
            "baseScore": 7.1,
            "baseSeverity": "HIGH",
            "confidentialityRequirement": "NOT_DEFINED",
            "exploitMaturity": "NOT_DEFINED",
            "integrityRequirement": "NOT_DEFINED",
            "modifiedAttackComplexity": "NOT_DEFINED",
            "modifiedAttackRequirements": "NOT_DEFINED",
            "modifiedAttackVector": "NOT_DEFINED",
            "modifiedPrivilegesRequired": "NOT_DEFINED",
            "modifiedSubAvailabilityImpact": "NOT_DEFINED",
            "modifiedSubConfidentialityImpact": "NOT_DEFINED",
            "modifiedSubIntegrityImpact": "NOT_DEFINED",
            "modifiedUserInteraction": "NOT_DEFINED",
            "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
            "modifiedVulnConfidentialityImpact": "NOT_DEFINED",
            "modifiedVulnIntegrityImpact": "NOT_DEFINED",
            "privilegesRequired": "LOW",
            "providerUrgency": "NOT_DEFINED",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "NONE",
            "userInteraction": "NONE",
            "valueDensity": "NOT_DEFINED",
            "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
            "version": "4.0",
            "vulnAvailabilityImpact": "HIGH",
            "vulnConfidentialityImpact": "NONE",
            "vulnIntegrityImpact": "NONE",
            "vulnerabilityResponseEffort": "NOT_DEFINED"
          },
          "source": "disclosure@vulncheck.com",
          "type": "Secondary"
        }
      ],
      "ssvcV203": [
        {
          "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "ssvcData": {
            "id": "CVE-2026-73321",
            "options": [
              {
                "exploitation": "poc"
              },
              {
                "automatable": "no"
              },
              {
                "technicalImpact": "partial"
              }
            ],
            "role": "CISA Coordinator",
            "timestamp": "2026-09-10T13:49:59.215010Z",
            "version": "2.0.3"
          }
        }
      ]
    },
    "published": "2026-09-08T14:17:26.617",
    "references": [
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Exploit",
          "Third Party Advisory"
        ],
        "url": "https://bombobombone.github.io/posts/cve-2026-73321/"
      },
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Exploit",
          "Third Party Advisory"
        ],
        "url": "https://github.com/BomboBombone/CVE-2026-73321"
      },
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Third Party Advisory"
        ],
        "url": "https://www.vulncheck.com/advisories/xenforo-uncontrolled-recursion-dos-via-bbcode-parser"
      },
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Release Notes"
        ],
        "url": "https://xenforo.com/community/threads/security-fixes-released-for-all-xenforo-and-media-gallery-versions-2-2-0-2-3-12.239856/"
      },
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Release Notes"
        ],
        "url": "https://xenforo.com/community/threads/xenforo-2-3-13-and-add-ons-released-includes-security-fixes.239857/"
      }
    ],
    "sourceIdentifier": "disclosure@vulncheck.com",
    "vulnStatus": "Analyzed",
    "weaknesses": [
      {
        "description": [
          {
            "lang": "en",
            "value": "CWE-674"
          }
        ],
        "source": "disclosure@vulncheck.com",
        "type": "Secondary"
      }
    ]
  }
}

—

Every claim, by kind

vulnerability

zetlyn/cve-nvd · 2026-09-08

automatable no cvss 6.5 cvss4 7.1 cvss4_vector CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X cvss_vector CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H cwe CWE-674 exploitation poc fixed_in 2.3.13 product XenForo severity MEDIUM status Analyzed technical_impact partial vendor XenForo

source