CVE Catalog

CVE-2026-73321

MediumCVSS 6.5
Published: Translated: NVD NIST

Summary

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.

Risk Assessment

Attackers can repeatedly submit malicious posts causing fatal errors that repeatedly terminate PHP-FPM workers, making the affected thread unavailable to all visitors.

Recommendation

Upgrade XenForo to version 2.3.13 or later which includes a fix to limit recursion depth.

Other vulnerabilities in XenForo

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Original NVD description (English source)

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.

Vulnerability data from NVD (NIST) · CISA KEV · EPSS