CVE-2026-73321
Medium
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.
SeverityMedium
CVSS6.5
Exploit probability—
Product
Xenforo
PublishedSep 8, 2026
First seenSep 8, 2026
Weakness typeCWE-674CWE-674
How to fix
Update
- xenforo xenforo2.3.13 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| xenforo xenforo | v < 2.3.13 | 2.3.13 |
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