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.
Published: 2026-03-05
Score: 7.5 High
EPSS: < 1% Very Low
KEV: No
Impact: n/a
Action: n/a
AI Analysis

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Remediation

No vendor fix or workaround currently provided.

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Tracking

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Advisories
Source ID Title
Github GHSA Github GHSA GHSA-5wmx-573v-2qwq Python-Markdown has an Uncaught Exception
History

Fri, 13 Mar 2026 01:30:00 +0000

Type Values Removed Values Added
CPEs cpe:2.3:a:python-markdown:markdown:3.8:*:*:*:*:python:*:*

Thu, 12 Mar 2026 17:15:00 +0000

Type Values Removed Values Added
Weaknesses CWE-400
Metrics 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'}

ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'poc', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}


Fri, 06 Mar 2026 21:30:00 +0000

Type Values Removed Values Added
References

Fri, 06 Mar 2026 15:30:00 +0000

Type Values Removed Values Added
First Time appeared Python-markdown
Python-markdown markdown
Vendors & Products Python-markdown
Python-markdown markdown

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

Subscriptions

Python-markdown Markdown
cve-icon MITRE

Status: PUBLISHED

Assigner: mitre

Published:

Updated: 2026-03-12T16:18:40.395Z

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

Link: CVE-2025-69534

cve-icon Vulnrichment

Updated: 2026-03-06T21:07:42.074Z

cve-icon NVD

Status : Analyzed

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

Modified: 2026-03-13T01:25:22.277

Link: CVE-2025-69534

cve-icon Redhat

Severity : Important

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

Links: CVE-2025-69534 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-03-06T15:18:21Z

Weaknesses