CVE-2026-59926

mediumCVSS 6.1covered by 2 sourcesfirst seen 2026-07-02

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.

CSIRTS triage

What: An XSS vulnerability exists via unescaped class option in the Admonition directive.
Who is affected: Users of Mistune are affected.
Urgency: Remediation is medium due to the medium severity of the vulnerability.
Action: Update to the latest version of Mistune.

AI-assisted analysis generated from the source advisory — verify against the original.

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Exploitation outlook

Low exploitation risk0.19% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 9% of all EPSS-scored CVEs.

Advisory coverage (2)

mediumCVE-2026-59926: Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.2.1, render_admonit…nvd · 2026-07-08
mediumCVE-2026-59926: Mistune: XSS via unescaped class option in Admonition directivemsrc · 2026-07-02

External references

NVD record for CVE-2026-59926

CVE.org record

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