{"id":"CVE-2026-59928","aliases":["GHSA-ffq3-xpv3-j92q","PYSEC-2026-2216"],"url":"https://o3.security/vulnerability/CVE-2026-59928","summary":"Mistune block_parser: quadratic-time parsing on long lists of repeated reference-link definitions","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.","published":"2026-07-08T16:23:21Z","modified":"2026-08-12T03:51:41.300968623Z","cvss":{"score":7.5,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"},"epss":null,"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"PyPI","name":"mistune","fixedVersion":"3.3.0"}],"fix":{"url":"https://github.com/lepture/mistune/commit/2b04d7ba341c16ac78fe82d3076bdd5c3de87c69","label":"lepture/mistune@2b04d7b"},"references":[{"type":"WEB","url":"https://github.com/lepture/mistune/releases/tag/v3.3.0"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/59xxx/CVE-2026-59928.json"},{"type":"ADVISORY","url":"https://github.com/lepture/mistune/security/advisories/GHSA-ffq3-xpv3-j92q"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-59928"},{"type":"FIX","url":"https://github.com/lepture/mistune/commit/2b04d7ba341c16ac78fe82d3076bdd5c3de87c69"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:41.300968623Z"}}