XenForo < 2.3.13 Uncontrolled Recursion DoS via BBCode Parser
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.
CVE-2026-73321
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: cve:CVE-2026-73321
XenForo
Source reference: /containers/cna/affected/0/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"vendor": "XenForo",
"product": "XenForo",
"versions": [
{
"status": "affected",
"version": "0",
"lessThan": "2.3.13",
"versionType": "semver"
}
],
"defaultStatus": "unaffected"
}
]- Related CVEs
- CVE-2026-73321
Source reference:
/cveMetadata/cveId
Publisher severity
high
Source reference: /containers/cna/metrics
- Event
- #5488 · Revision 1
- Added to Heist Feed
- Publisher date