Denial of Service in Python-Markdown Through Malformed HTML Sequences
CVE-2025-69534

7.5HIGH

Key Information:

Vendor

Python-Markdown

Status
Python-Markdown
Vendor
CVE Published:
5 March 2026

What is CVE-2025-69534?

A vulnerability in Python-Markdown version 3.8 allows malformed HTML-like sequences to trigger an unhandled AssertionError during Markdown parsing. This failure to manage exceptions can lead to a remote Denial of Service in various applications that render Markdown, including web applications, documentation systems, and CI/CD pipelines. The issue, which was acknowledged by the vendor, has been resolved in version 3.8.1, emphasizing the importance of validating Markdown content in scenarios involving untrusted input to prevent exploitation and potential information disclosure.

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References

https://github.com/Python-Markdown/markdown/issues/1534
https://github.com/Python-Markdown/markdown
https://github.com/Python-Markdown/markdown/actions/runs/...

CVSS V3.1

Score:
7.5
Severity:
HIGH
Confidentiality:
None
Integrity:
None
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

JSON
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