GitHub Advisoryadvisory · PyPI
GHSA-5wmx-573v-2qwq Python-Markdown has an Uncaught Exception
MEDIUM
Official page ↗
- Aliases
- CVE-2025-69534
- Ecosystem
- PyPI
- Packages
- Markdown
- Severity
- Moderate
- CVSS vector
- CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- Weaknesses
- CWE-248, CWE-400
- Reviewed
- 2026-03-05
Affected packages
• PyPI Markdown: < 3.8.1 → fixed in 3.8.1
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.
Related
Alias · CVE (1)
- CVE-2025-69534 Python-Markdown version 3.8 contain a vulnerability where malformed HTML-like sequences can cause html.parser.HTMLParser to raise an… vulnerability
References
- https://nvd.nist.gov/vuln/detail/CVE-2025-69534 advisory
- https://github.com/Python-Markdown/markdown/issues/1534 web
- https://github.com/Python-Markdown/markdown/pull/1535 web
- https://github.com/Python-Markdown/markdown web
- https://github.com/Python-Markdown/markdown/actions/runs/15736122892 web
- https://github.com/pypa/advisory-database/tree/main/vulns/markdown/PYSEC-2026-89.yaml web
- http://www.openwall.com/lists/oss-security/2026/03/06/4 web