CVE-2026-73321
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XenForo 2.3.13 Uncontrolled Recursion in BBCode Parser
Vulnerability report for CVE-2026-73321, including description, CVSS score, EPSS score, affected products, exploitability, helpful resources, and attack-flow context.
Publication date: 2026-09-08
Last updated on: 2026-09-09
Assigner: VulnCheck
Description
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.
CVSS Scores
EPSS Scores
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Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| xenforo | xenforo | to 2.3.13 (exc) |
Helpful Resources
Exploitability
CWE
KEV
| CWE ID | Description |
|---|---|
| CWE-674 | The product does not properly control the amount of recursion that takes place, consuming excessive resources, such as allocated memory or the program stack. |
