CVE-2026-59930: Mistune Project Mistune

Medium severity, CVSS 4.3. EPSS: 0.2% chance of exploitation in the next 30 days.

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.

Affected products

• Mistune Project Mistune: before 3.3.0 (fixed in 3.3.0)

Published 2026-07-08. Last modified 2026-07-09.