{"affected":[{"defaultStatus":"unaffected","ecosystem":"pypi","packageName":"mistune","product":"mistune","source":"CNA: VulnCheck","vendor":"lepture","versions":[{"lessThan":"3.3.3","status":"affected","version":"0","versionType":"semver"},{"status":"unaffected","version":"3.3.3","versionType":"semver"}]}],"cveId":"CVE-2026-121438","cwes":["CWE-400"],"description":"Mistune before 3.3.3 contains a denial of service vulnerability in InlineParser.parse_link that allows attackers to cause quadratic CPU growth by supplying balanced nested brackets. Attackers can submit crafted Markdown with thousands of nested bracket pairs not forming a valid link, triggering repeated _contains_nested_link scans that exhaust CPU in parsing applications.","epss":null,"exploits":[],"kev":null,"metrics":[{"score":6.9,"severity":"medium","source":"CNA: VulnCheck","vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N","version":"4.0"},{"score":5.3,"severity":"medium","source":"CNA: VulnCheck","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","version":"3.1"}],"modifiedAt":1793716109879,"publishedAt":1793716109879,"references":[{"source":"CNA: VulnCheck","tags":["vendor-advisory"],"url":"https://github.com/lepture/mistune/security/advisories/GHSA-47p6-w2rc-5qf7"},{"source":"CNA: VulnCheck","tags":["patch"],"url":"https://github.com/lepture/mistune/commit/fe02f40faf091f86da9ed62c865f31e11da111d7"},{"source":"CNA: VulnCheck","tags":["third-party-advisory"],"url":"https://www.vulncheck.com/advisories/mistune-before-3.3.3-denial-of-service-via-balanced-bracket-link-parsing"}],"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/fe02f40faf091f86da9ed62c865f31e11da111d7"}],"revision":"c4ce2689a6d4d5f75dd0098f3244b8519d02e28fcf908cb1f7549902efae5656","sources":[{"modifiedAt":1793716109879,"name":"CNA: VulnCheck","retrievedAt":1793718590465,"url":"https://www.cve.org/CVERecord?id=CVE-2026-121438"}],"ssvc":null,"status":"published","title":"Mistune before 3.3.3 Denial of Service via Balanced Bracket Link Parsing","updatedAt":1793718590465}