{"id":"CVE-2026-73321","aliases":["EUVD-2026-72758","GHSA-vv8x-44ww-j3wh"],"status":"published","title":"XenForo \u003c 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.","severity":{"version":"4.0","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","level":"high","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-12","score":0.00614,"percentile":0.49947,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":true,"fix_available":false},"cwes":["CWE-674"],"published":"2026-09-08T13:20:16Z","modified":"2026-10-01T15:20:39Z","exploits":[{"source":"pocgithub","id":"BomboBombone/CVE-2026-73321","title":"BomboBombone/CVE-2026-73321","date":"2026-09-08","url":"https://github.com/BomboBombone/CVE-2026-73321"}],"products":[{"vendor":"xenforo","product":"xenforo"}],"references":[{"url":"https://xenforo.com/community/threads/security-fixes-released-for-all-xenforo-and-media-gallery-versions-2-2-0-2-3-12.239856/","tags":["vendor-advisory","patch","Release Notes"]},{"url":"https://xenforo.com/community/threads/xenforo-2-3-13-and-add-ons-released-includes-security-fixes.239857/","tags":["release-notes","Release Notes"]},{"url":"https://bombobombone.github.io/posts/cve-2026-73321/","tags":["technical-description","Exploit","Third Party Advisory"]},{"url":"https://github.com/BomboBombone/CVE-2026-73321","tags":["exploit","Exploit","Third Party Advisory"]},{"url":"https://www.vulncheck.com/advisories/xenforo-uncontrolled-recursion-dos-via-bbcode-parser","tags":["third-party-advisory","Third Party Advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-73321"},{"url":"https://xenforo.com/community/threads/security-fixes-released-for-all-xenforo-and-media-gallery-versions-2-2-0-2-3-12.239856"},{"url":"https://xenforo.com/community/threads/xenforo-2-3-13-and-add-ons-released-includes-security-fixes.239857"},{"url":"https://bombobombone.github.io/posts/cve-2026-73321"},{"url":"https://github.com/advisories/GHSA-vv8x-44ww-j3wh"}],"sources":{"cve":[{"id":"CVE-2026-73321","title":"XenForo \u003c 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.","status":"published","published":"2026-09-08T13:20:16.081Z","modified":"2026-10-01T15:20:39.261Z","cvss":[{"version":"4.0","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","level":"high","assessor":"cna"},{"version":"3.1","score":6.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","level":"medium","assessor":"cna"}],"cwes":["CWE-674"],"updated_at":"2026-11-02T13:43:33.766176Z"}],"euvd":[{"id":"EUVD-2026-72758","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.","status":"published","published":"2026-09-08T13:20:16Z","modified":"2026-10-01T15:20:39Z","cvss":[{"version":"4.0","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","level":"high"}],"updated_at":"2026-11-02T17:27:45.017929Z"}],"ghsa":[{"id":"GHSA-vv8x-44ww-j3wh","title":"XenForo before 2.3.13 contains an uncontrolled recursion vulnerability in the BBCode parser that...","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.","status":"published","published":"2026-09-08T15:31:55Z","modified":"2026-09-09T03:30:37Z","cvss":[{"version":"3.1","score":6.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","level":"medium"},{"version":"4.0","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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"high"}],"cwes":["CWE-674"],"updated_at":"2026-11-02T15:11:37.523128Z"}],"nvd":[{"id":"CVE-2026-73321","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.","status":"published","published":"2026-09-08T14:17:26.617Z","modified":"2026-09-11T20:30:18.293Z","cvss":[{"version":"4.0","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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"high","assessor":"secondary"},{"version":"3.1","score":6.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","level":"medium","assessor":"secondary"}],"cwes":["CWE-674"],"updated_at":"2026-11-02T14:12:44.436435Z"}]}}