EUVD-2026-72758
GHSA-vv8x-44ww-j3wh
Severity by source
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
Scope change applies because one authenticated user's post crashes PHP-FPM workers for all other visitors; no confidentiality or integrity impact.
Primary rating from Vendor (VulnCheck).
CVSS VectorVendor: VulnCheck
Lifecycle Timeline
2DescriptionCVE.org
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.
AnalysisAI
Persistent denial-of-service in XenForo's BBCode parser allows any authenticated forum member to crash PHP-FPM workers for all visitors by submitting a single post with sufficiently deep BBCode nesting. The recursive parser exhausts PHP's call stack, generating fatal errors that terminate worker processes - and because the malicious post persists in the database, every subsequent render of the affected thread repeats the crash, sustaining the outage until the post is removed or the forum is patched. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | The attacker must possess a registered XenForo forum account with standard post-creation privileges (PR:L); no moderator or administrator rights are required. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 4.0 vector (AV:N/AC:L/AT:N/PR:L/UI:N/VA:H) accurately captures the threat profile: network-accessible, no special configuration needed, only a standard registered account required, and high availability impact. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | Full exploit scenario with step-by-step reproduction available after sign-in. |
| Remediation | Upgrade to XenForo 2.3.13 or later; the release announcement is at https://xenforo.com/community/threads/xenforo-2-3-13-and-add-ons-released-includes-security-fixes.239857/ and the security advisory at https://xenforo.com/community/threads/security-fixes-released-for-all-xenforo-and-media-gallery-versions-2-2-0-2-3-12.239856/. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, identify all XenForo installations in your environment and verify current versions. …
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Same weakness CWE-674 – Uncontrolled Recursion
View allSame technique Denial Of Service
View allShare
External POC / Exploit Code
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