{"id":"CVE-2026-44898","aliases":["GHSA-6269-cqxg-mhhv","PYSEC-2026-2208"],"url":"https://o3.security/vulnerability/CVE-2026-44898","summary":"Mistune TOC Anchor Injection XSS","details":"Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.2.1, render_toc_ul() builds a <ul> table-of-contents tree from a list of (level, id, text) tuples. Both the id value (used as href=\"#<id>\") and the text value (used as the visible link label) are inserted into <a> tags via a plain Python format string — with no HTML escaping applied to either value. When heading IDs are derived from user-supplied heading text (the standard use-case for readable slug anchors), an attacker can craft a heading whose text breaks out of the href=\"#...\" attribute context, injecting arbitrary HTML tags including <script> blocks directly into the rendered TOC. This vulnerability is fixed in 3.2.1.","published":"2026-05-26T20:41:53.805Z","modified":"2026-08-07T11:49:50.652702200Z","cvss":{"score":6.1,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N"},"epss":{"score":0.00228,"percentile":0.13578,"asOf":"2026-08-10"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"PyPI","name":"mistune","fixedVersion":"3.2.1"}],"fix":null,"references":[{"type":"WEB","url":"https://github.com/lepture/mistune/releases/tag/v3.2.1"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/44xxx/CVE-2026-44898.json"},{"type":"ADVISORY","url":"https://github.com/lepture/mistune/security/advisories/GHSA-6269-cqxg-mhhv"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-44898"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-07T11:49:50.652702200Z"}}