CVE-2026-59930

MEDIUM4.3

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

Published Jul 8, 2026

Modified 2 weeks ago

Details

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.

References

WEB

https://github.com/lepture/mistune/commit/c4093c4742ed0d10d9332fb8edb455869b7b581b

WEB

https://github.com/lepture/mistune/releases/tag/v3.3.0

WEB

https://github.com/lepture/mistune/security/advisories/GHSA-2hm2-hc3v-44h9

ADVISORY

https://www.cve.org/CVERecord?id=CVE-2026-59930

CVSS Analysis

CVSS v3.1

4.3