{"id":"PYSEC-2026-2216","details":"Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, a Markdown document containing many repeated or distinct reference-link definitions causes quadratic work in src/mistune/block_parser.py and the ref_links environment dictionary handling, allowing denial of service through CPU exhaustion. This issue is fixed in version 3.3.0.","aliases":["CVE-2026-59928","GHSA-ffq3-xpv3-j92q"],"modified":"2026-07-13T07:15:18.812243616Z","published":"2026-07-08T17:17:28.600Z","references":[{"type":"ADVISORY","url":"https://github.com/lepture/mistune/releases/tag/v3.3.0"},{"type":"FIX","url":"https://github.com/lepture/mistune/commit/2b04d7ba341c16ac78fe82d3076bdd5c3de87c69"},{"type":"EVIDENCE","url":"https://github.com/lepture/mistune/security/advisories/GHSA-ffq3-xpv3-j92q"}],"affected":[{"package":{"name":"mistune","ecosystem":"PyPI","purl":"pkg:pypi/mistune"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"3.3.0"}]}],"versions":["0.1.0","0.2.0","0.3.0","0.3.1","0.4","0.4.1","0.5","0.5.1","0.6","0.7","0.7.1","0.7.2","0.7.3","0.7.4","0.8","0.8.1","0.8.2","0.8.3","0.8.4","2.0.0","2.0.0a1","2.0.0a2","2.0.0a3","2.0.0a4","2.0.0a5","2.0.0a6","2.0.0rc1","2.0.1","2.0.2","2.0.3","2.0.4","2.0.5","2.1.0","3.0.0","3.0.0a1","3.0.0a2","3.0.0a3","3.0.0rc1","3.0.0rc2","3.0.0rc3","3.0.0rc4","3.0.0rc5","3.0.1","3.0.2","3.1.0","3.1.1","3.1.2","3.1.3","3.1.4","3.2.0","3.2.1"],"ecosystem_specific":{},"database_specific":{"source":"https://github.com/pypa/advisory-database/blob/main/vulns/mistune/PYSEC-2026-2216.yaml"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"}]}