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.

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History

Fri, 11 Sep 2026 23:45:00 +0000

Type Values Removed Values Added
CPEs cpe:2.3:a:xenforo:xenforo:*:*:*:*:*:*:*:*

Thu, 10 Sep 2026 15:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'poc', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Wed, 09 Sep 2026 01:15:00 +0000


Tue, 08 Sep 2026 15:00:00 +0000

Type Values Removed Values Added
First Time appeared Xenforo
Xenforo xenforo
Vendors & Products Xenforo
Xenforo xenforo

Tue, 08 Sep 2026 13:30:00 +0000

Type Values Removed Values Added
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.
Title XenForo < 2.3.13 Uncontrolled Recursion DoS via BBCode Parser
Weaknesses CWE-674
References
Metrics cvssV3_1

{'score': 6.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'}

cvssV4_0

{'score': 7.1, 'vector': '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'}


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cve-icon MITRE

Status: PUBLISHED

Assigner: VulnCheck

Published:

Updated: 2026-09-10T15:02:59.382Z

Reserved: 2026-08-11T19:56:20.008Z

Link: CVE-2026-73321

cve-icon Vulnrichment

Updated: 2026-09-10T13:50:08.414Z

cve-icon NVD

Status : Analyzed

Published: 2026-09-08T14:17:26.617

Modified: 2026-09-11T20:30:18.293

Link: CVE-2026-73321

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-09-08T15:15:17Z

Weaknesses