{"id":"CVE-2026-73321","revision":"0b97b5909272447bab0375c4ccbfd65c","records":[{"revision":"0b97b5909272447bab0375c4ccbfd65c","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-73321","aliases":[],"title":"XenForo < 2.3.13 Uncontrolled Recursion DoS via BBCode Parser","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.","state":0,"publishedAt":"2026-09-08T13:20:16.081+00:00","modifiedAt":"2026-10-01T15:20:39.261+00:00","affected":[{"ecosystem":"Vendor product","name":"XenForo","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"defaultStatus\": \"unaffected\",\n                    \"vendor\": \"XenForo\",\n                    \"product\": \"XenForo\",\n                    \"versions\": [\n                        {\n                            \"status\": \"affected\",\n                            \"version\": \"0\",\n                            \"versionType\": \"semver\",\n                            \"lessThan\": \"2.3.13\"\n                        }\n                    ]\n                }"}],"metrics":[{"system":"CVSS 4.0","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","score":7.1,"severity":"HIGH"},{"system":"CVSS 3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","score":6.5,"severity":"MEDIUM"}],"references":["https://xenforo.com/community/threads/security-fixes-released-for-all-xenforo-and-media-gallery-versions-2-2-0-2-3-12.239856/","https://xenforo.com/community/threads/xenforo-2-3-13-and-add-ons-released-includes-security-fixes.239857/","https://bombobombone.github.io/posts/cve-2026-73321/","https://github.com/BomboBombone/CVE-2026-73321","https://www.vulncheck.com/advisories/xenforo-uncontrolled-recursion-dos-via-bbcode-parser"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-73321","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-73321","identifiers":["CVE-2026-73321"]},"retained":false,"historicalAffected":[]}],"coverage":[]}