{"id":"CVE-2026-121438","published":"2026-11-03T15:17:35.330","lastModified":"2026-11-03T15:17:35.457","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.","cvssScore":5.3,"cvssSeverity":"MEDIUM","cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","cwes":["CWE-400"],"vendors":[],"products":[],"references":[{"url":"https://github.com/lepture/mistune/commit/fe02f40faf091f86da9ed62c865f31e11da111d7","tags":[]},{"url":"https://github.com/lepture/mistune/security/advisories/GHSA-47p6-w2rc-5qf7","tags":[]},{"url":"https://www.vulncheck.com/advisories/mistune-before-3.3.3-denial-of-service-via-balanced-bracket-link-parsing","tags":[]}],"exploitRefs":[{"url":"https://github.com/lepture/mistune/commit/fe02f40faf091f86da9ed62c865f31e11da111d7","tags":[]},{"url":"https://github.com/lepture/mistune/security/advisories/GHSA-47p6-w2rc-5qf7","tags":[]}],"hasPoc":true,"ai":null}