CVE-2025-69534

Description

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.

Predictions

Heuristic predictions, AS-IS, for prioritization only.

Mitigations

References

• https://nvd.nist.gov/vuln/detail/CVE-2025-69534
• https://github.com/Python-Markdown/markdown/issues/1534
• https://github.com/Python-Markdown/markdown/pull/1535
• https://github.com/Python-Markdown/markdown
• https://github.com/Python-Markdown/markdown/actions/runs/15736122892
• http://www.openwall.com/lists/oss-security/2026/03/06/4
• https://access.redhat.com/errata/RHSA-2026:19366
• https://www.suse.com/security/cve/CVE-2025-69534.html
• https://security-tracker.debian.org/tracker/CVE-2025-69534