CVE-2026-59930 | Mistune is a Python Markdown parser with renderers and plugi… | CVSS 4.3 MEDIUM

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.

Metadata

CVE ID: CVE-2026-59930
State: PUBLISHED
Assigner: GitHub_M
Reserved: 2026-07-07 18:20 UTC
Published: 2026-07-08 16:13 UTC
Last updated: 2026-07-08 16:13 UTC
Primary CWE: CWE-345
CWE-345: Insufficient Verification of Data Authenticity
Vendor / Product: lepture / mistune
Sources: cve.org · NVD

Severity & Metrics

4.3 MEDIUM CVSS 3.1

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N

Affected products (1)

Vendor	Product	Platform	Versions
lepture	mistune	—	< 3.3.0

Weakness (CWE)

CWE	Source	Description
CWE-1284	cna	CWE-1284: Improper Validation of Specified Quantity in Input
CWE-345	cna	CWE-345: Insufficient Verification of Data Authenticity

CVSS scores (1)

Score	Severity	Version	Source	Vector
4.3	MEDIUM	3.1	cna	CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N

References (3)

https://github.com/lepture/mistune/security/advisories/GHSA-2hm2-hc3v-44h9 https://github.com/lepture/mistune/security/advisories/GHSA-2hm2-hc3v-44h9
https://github.com/lepture/mistune/commit/c4093c4742ed0d10d9332fb8edb455869b7b581b https://github.com/lepture/mistune/commit/c4093c4742ed0d10d9332fb8edb455869b7b581b
https://github.com/lepture/mistune/releases/tag/v3.3.0 https://github.com/lepture/mistune/releases/tag/v3.3.0