{"affected":[{"defaultStatus":"unaffected","ecosystem":"pypi","packageName":"mistune","product":"mistune","source":"CNA: VulnCheck","vendor":"lepture","versions":[{"lessThan":"3.3.4","status":"affected","version":"3.3.0","versionType":"semver"},{"status":"unaffected","version":"3.3.4","versionType":"semver"}]}],"cveId":"CVE-2026-121437","cwes":["CWE-407"],"description":"Mistune from 3.3.0 before 3.3.4 contains a denial of service vulnerability that allows remote attackers to exhaust CPU through quadratic-time emphasis delimiter processing. Attackers can submit small markdown documents with repeated patterns like \"*a_b\" to trigger an O(n²) index-fixup loop, stalling workers for seconds.","epss":null,"exploits":[{"kind":"exploit","source":"ADP: CISA-ADP","url":"https://github.com/lepture/mistune/security/advisories/GHSA-qp42-r9j6-83g9"}],"kev":null,"metrics":[{"score":8.7,"severity":"high","source":"CNA: VulnCheck","vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N","version":"4.0"},{"score":7.5,"severity":"high","source":"CNA: VulnCheck","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","version":"3.1"}],"modifiedAt":1793725157405,"publishedAt":1793716109178,"references":[{"source":"CNA: VulnCheck","tags":["vendor-advisory"],"url":"https://github.com/lepture/mistune/security/advisories/GHSA-qp42-r9j6-83g9"},{"source":"CNA: VulnCheck","tags":["patch"],"url":"https://github.com/lepture/mistune/commit/b4dd3284e52ec741ed9a227db29ade9017828e90"},{"source":"CNA: VulnCheck","tags":["third-party-advisory"],"url":"https://www.vulncheck.com/advisories/mistune-3.3.0-before-3.3.4-quadratic-time-dos-via-process-emphasis-delimiters"},{"source":"ADP: CISA-ADP","tags":["exploit"],"url":"https://github.com/lepture/mistune/security/advisories/GHSA-qp42-r9j6-83g9"}],"remediation":[{"kind":"fix","source":"CNA: VulnCheck","text":"The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches.","url":"https://github.com/lepture/mistune/commit/b4dd3284e52ec741ed9a227db29ade9017828e90"}],"revision":"9d27b439289a8a4d2879bb313caf1ca819e33cd2ba45c69385c0544c1bfedcea","sources":[{"modifiedAt":1793725157405,"name":"CNA: VulnCheck","retrievedAt":1793725903924,"url":"https://www.cve.org/CVERecord?id=CVE-2026-121437"}],"ssvc":{"assessedAt":1793725105525,"automatable":"no","exploitation":"poc","source":"ADP: CISA-ADP","technicalImpact":"partial"},"status":"published","title":"Mistune 3.3.0 before 3.3.4 Quadratic-Time DoS via _process_emphasis_delimiters","updatedAt":1793725903924}