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  5. CVE-2025-69534

CVE-2025-69534: Python-Markdown has an Uncaught Exception

March 5, 2026 (updated March 12, 2026)

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

  • github.com/Python-Markdown/markdown
  • github.com/Python-Markdown/markdown/actions/runs/15736122892
  • github.com/Python-Markdown/markdown/issues/1534
  • github.com/Python-Markdown/markdown/pull/1535
  • github.com/advisories/GHSA-5wmx-573v-2qwq
  • nvd.nist.gov/vuln/detail/CVE-2025-69534

Code Behaviors & Features

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Affected versions

All versions before 3.8.1

Fixed versions

  • 3.8.1

Solution

Upgrade to version 3.8.1 or above.

Impact 7.5 HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Learn more about CVSS

Weakness

  • CWE-248: Uncaught Exception
  • CWE-400: Uncontrolled Resource Consumption

Source file

pypi/Markdown/CVE-2025-69534.yml

Spotted a mistake? Edit the file on GitLab.

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