Mistune: XSS via unescaped class option in Admonition directive
CVE-2026-59926 is fixed in 2 products on 1 platform, first by DEBIAN-CVE-2026-59926, released July 8, 2026. It is not reported as exploited. Patch Radar priority: Routine.
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.
Where it's fixed
| Product | Fixed in | Fix | Released |
|---|---|---|---|
| Linux | |||
| mistune · Debian 14 | 3.1.4-1 | DEBIAN-CVE-2026-59926 | Jul 8, 2026 |
| python-mistune · opensuse-leap 16.0 | 3.1.3-160000.5.1 | OPENSUSE-SU-2026:21339-1 | Jul 14, 2026 |
| python-mistune · sles 16.0 | 3.1.3-160000.5.1 | SUSE-SU-2026:22655-1 | Jul 14, 2026 |
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