{"id":"GHSA-g97x-gvcm-x72h","summary":"Mistune: XSS via unescaped class option in Admonition directive","details":"In `src/mistune/directives/admonition.py`, the `render_admonition()` function concatenates the `:class:` option directly into the HTML class attribute without escaping (lines 63-68).\n\nThis allows attribute injection and XSS even when `HTMLRenderer(escape=True)` is used.\n\nThe directive name parameter is safe (validated against whitelist), but the class option comes from raw user input.","aliases":["CVE-2026-59926","PYSEC-2026-2214"],"modified":"2026-07-20T21:46:40.316164045Z","published":"2026-07-20T21:34:14Z","database_specific":{"nvd_published_at":"2026-07-08T17:17:28Z","cwe_ids":["CWE-79"],"severity":"MODERATE","github_reviewed":true,"github_reviewed_at":"2026-07-20T21:34:14Z"},"references":[{"type":"WEB","url":"https://github.com/lepture/mistune/security/advisories/GHSA-g97x-gvcm-x72h"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-59926"},{"type":"WEB","url":"https://github.com/lepture/mistune/commit/a3cb6e5655308797e8be021d6c7b5bab13cbace2"},{"type":"PACKAGE","url":"https://github.com/lepture/mistune"},{"type":"WEB","url":"https://github.com/lepture/mistune/releases/tag/v3.2.1"},{"type":"WEB","url":"https://github.com/pypa/advisory-database/tree/main/vulns/mistune/PYSEC-2026-2214.yaml"}],"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"],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/07/GHSA-g97x-gvcm-x72h/GHSA-g97x-gvcm-x72h.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N"}]}