CVE-2026-73321
XenForo < 2.3.13 Uncontrolled Recursion DoS via BBCode Parser
- State
- Published
- Severity
- 7.1 High
- Published
- Sep 8, 2026
- Updated
- Oct 1, 2026
- Reserved
- Aug 11, 2026
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 4.0 | 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 | VulnCheck |
| 3.1 | 6.5 Medium | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H | VulnCheck |
Weaknesses
- CWE-674 Uncontrolled Recursion
Affected Products
| Product | Versions |
|---|---|
XenForoXenForo |
|
References
- Vendor Advisoryvendor-advisorypatch
- Release Notesrelease-notes
- Researcher Advisorytechnical-description
- Researcher PoCexploit
- https://www.vulncheck.com/advisories/xenforo-uncontrolled-recursion-dos-via-bbcode-parserthird-party-advisory
Every record here comes from the CVE Program’s CVE List. © 1999–2026 The MITRE Corporation. CVE is a registered trademark of The MITRE Corporation. The records are reproduced under the CVE Program terms of use.