CVE-2026-59930 – Mistune toc / TableOfContents directive: heading IDs use predictable `toc_N` numbering with no slugification, allowing collision with attacker-controlled `id=”toc_N”` content

CVE ID :CVE-2026-59930

Published : July 8, 2026, 5:17 p.m. | 31 minutes ago

Description :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.

Severity: 4.3 | MEDIUM

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