CVE-2026-59930

mediumCVSS 4.3covered by 2 sourcesfirst seen 2026-07-02

Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, the toc plugin and TableOfContents directive generate heading IDs as predictable toc_N values without slugifying the heading text, allowing attacker-controlled id="toc_N" content to collide with generated anchors and redirect same-page navigation, CSS selectors, or JavaScript handlers. This issue is fixed in version 3.3.0.

CSIRTS triage

What: The TableOfContents directive allows for predictable heading IDs that can collide with attacker-controlled content.
Who is affected: Users of Mistune are affected by this vulnerability.
Urgency: Remediation is necessary as it poses a medium severity risk.
Action: Consider updating to a patched version of Mistune when available.

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

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Exploitation outlook

Low exploitation risk0.13% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 3% of all EPSS-scored CVEs.

Advisory coverage (2)

mediumCVE-2026-59930: Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, the toc plugin…nvd · 2026-07-08
mediumCVE-2026-59930: Mistune toc / TableOfContents directive: heading IDs use predictable `toc_N` numbering with no…msrc · 2026-07-02

External references

NVD record for CVE-2026-59930

CVE.org record

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