{"id":"PYSEC-2026-89","details":"Python-Markdown version 3.8 contain a vulnerability where malformed HTML-like sequences can cause html.parser.HTMLParser to raise an unhandled AssertionError during Markdown parsing. Because Python-Markdown does not catch this exception, any application that processes attacker-controlled Markdown may crash. This enables remote, unauthenticated Denial of Service in web applications, documentation systems, CI/CD pipelines, and any service that renders untrusted Markdown. The issue was acknowledged by the vendor and fixed in version 3.8.1. This issue causes a remote Denial of Service in any application parsing untrusted Markdown, and can lead to Information Disclosure through uncaught exceptions.","aliases":["CVE-2025-69534","GHSA-5wmx-573v-2qwq"],"modified":"2026-05-21T15:00:15.862067676Z","published":"2026-03-05T15:16:11.243Z","references":[{"type":"WEB","url":"https://github.com/Python-Markdown/markdown/actions/runs/15736122892"},{"type":"ADVISORY","url":"http://www.openwall.com/lists/oss-security/2026/03/06/4"},{"type":"REPORT","url":"https://github.com/Python-Markdown/markdown/issues/1534"},{"type":"PACKAGE","url":"https://github.com/Python-Markdown/markdown"}],"affected":[{"package":{"name":"markdown","ecosystem":"PyPI","purl":"pkg:pypi/markdown"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"last_affected":"3.8"}]}],"versions":["1.7","2.0","2.0.1","2.0.2","2.0.3","2.1.0","2.1.1","2.2.0","2.2.1","2.3","2.3.1","2.4","2.4.1","2.5","2.5.1","2.5.2","2.6","2.6.1","2.6.10","2.6.11","2.6.2","2.6.3","2.6.4","2.6.5","2.6.6","2.6.7","2.6.8","2.6.9","3.0","3.0.1","3.1","3.1.1","3.2","3.2.1","3.2.2","3.3","3.3.1","3.3.2","3.3.3","3.3.4","3.3.5","3.3.6","3.3.7","3.4","3.4.1","3.4.2","3.4.3","3.4.4","3.5","3.5.1","3.5.2","3.6","3.7","3.8"],"ecosystem_specific":{},"database_specific":{"source":"https://github.com/pypa/advisory-database/blob/main/vulns/markdown/PYSEC-2026-89.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"}]}