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.
History

Fri, 06 Mar 2026 00:15:00 +0000

Type Values Removed Values Added
Title python-markdown: denial of service via malformed HTML-like sequences
Weaknesses CWE-617
References
Metrics threat_severity

None

cvssV3_1

{'score': 8.2, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H'}

threat_severity

Important


Thu, 05 Mar 2026 15:15:00 +0000

Type Values Removed Values Added
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.
References

cve-icon MITRE

Status: PUBLISHED

Assigner: mitre

Published: 2026-03-05T00:00:00.000Z

Updated: 2026-03-05T14:54:49.592Z

Reserved: 2026-01-09T00:00:00.000Z

Link: CVE-2025-69534

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Awaiting Analysis

Published: 2026-03-05T15:16:11.243

Modified: 2026-03-05T19:38:33.877

Link: CVE-2025-69534

cve-icon Redhat

Severity : Important

Publid Date: 2026-03-05T00:00:00Z

Links: CVE-2025-69534 - Bugzilla