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Medium · 6.5 Public exploit CVE-2026-73321 EUVD-2026-72758GHSA-vv8x-44ww-j3wh

XenForo < 2.3.13 Uncontrolled Recursion DoS via BBCode Parser

Published Sep 8, 2026 · Updated Oct 1, 2026 · Assigned by VulnCheck

Vendor: XenForo Product: XenForo

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 products

VendorProductAffectedFixed
XenForo XenForo < 2.3.13 2.3.13

Public exploits

Exploit or proof-of-concept code for this vulnerability is publicly available, which lowers the bar for attackers. Treat it as a reason to patch sooner.

Third-party code, not reviewed by us. Public PoCs are sometimes fake or contain malware. Read the code first and run it only in an isolated lab, against systems you are authorised to test.

GitHub 1 repository

Sources: PoC-in-GitHub, Metasploit Framework, Exploit-DB — updated daily. Only links are listed; no exploit code is hosted here.

References