CVEvulnerability
CVE-2026-73321
7.1 HIGH
Official page ↗
- Status
- Analyzed
- Published
- 2026-09-08
- Last modified
- 2026-09-11
- Assigner
- [email protected]
- CVSS 4.0 ([email protected])
- 7.1 HIGH — 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 3.1 ([email protected])
- 6.5 MEDIUM — CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- Weaknesses
- CWE-674
Description
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.
Affected configurations
• xenforo xenforo (< 2.3.13)
Related
Weakness · CWE (1)
- CWE-674 Uncontrolled Recursion weakness
References
- https://bombobombone.github.io/posts/cve-2026-73321/ Exploit, Third Party Advisory
- https://github.com/BomboBombone/CVE-2026-73321 Exploit, Third Party Advisory
- https://www.vulncheck.com/advisories/xenforo-uncontrolled-recursion-dos-via-bbcode-parser Third Party Advisory
- https://xenforo.com/community/threads/security-fixes-released-for-all-xenforo-and-media-gallery-versions-2-2-0-2-3-12.239856/ Release Notes
- https://xenforo.com/community/threads/xenforo-2-3-13-and-add-ons-released-includes-security-fixes.239857/ Release Notes