CVE-2026-59926

MEDIUM6.1

Mistune: XSS via unescaped class option in Admonition directive

Published Jul 8, 2026

Modified 2 weeks ago

Details

Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.2.1, render_admonition() in src/mistune/directives/admonition.py concatenates the Admonition directive :class: option into the HTML class attribute without escaping, allowing attribute injection and cross-site scripting even when HTMLRenderer escape mode is enabled. This issue is fixed in version 3.2.1.

References

WEB

https://github.com/lepture/mistune/commit/a3cb6e5655308797e8be021d6c7b5bab13cbace2

WEB

https://github.com/lepture/mistune/releases/tag/v3.2.1

WEB

https://github.com/lepture/mistune/security/advisories/GHSA-g97x-gvcm-x72h

ADVISORY

https://www.cve.org/CVERecord?id=CVE-2026-59926

CVSS Analysis

CVSS v4.0

5.3