CVE-2026-59926 | Mistune is a Python Markdown parser with renderers and plugi… | CVSS 5.3 MEDIUM

Description

Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.2.1, render_admonition() in src/mistune/directives/admonition.py concatenates the Admonition directive :class: option into the HTML class attribute without escaping, allowing attribute injection and cross-site scripting even when HTMLRenderer escape mode is enabled. This issue is fixed in version 3.2.1.

Metadata

CVE ID: CVE-2026-59926
State: PUBLISHED
Assigner: GitHub_M
Reserved: 2026-07-07 18:20 UTC
Published: 2026-07-08 16:16 UTC
Last updated: 2026-07-08 19:40 UTC
Primary CWE: CWE-79
CWE-79: Improper Neutralization of Input During Web Page Gen…
Vendor / Product: lepture / mistune
Sources: cve.org · NVD

Severity & Metrics

5.3 MEDIUM CVSS 4.0

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N

SSVC — CISA Coordinator

Exploitation: none
Automatable: no
Tech. Impact: partial

Affected products (1)

Vendor	Product	Platform	Versions
lepture	mistune	—	< 3.2.1

Weakness (CWE)

CWE	Source	Description
CWE-79	cna	CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

CVSS scores (1)

Score	Severity	Version	Source	Vector
5.3	MEDIUM	4.0	cna	CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N

References (3)

https://github.com/lepture/mistune/security/advisories/GHSA-g97x-gvcm-x72h https://github.com/lepture/mistune/security/advisories/GHSA-g97x-gvcm-x72h
https://github.com/lepture/mistune/commit/a3cb6e5655308797e8be021d6c7b5bab13cbace2 https://github.com/lepture/mistune/commit/a3cb6e5655308797e8be021d6c7b5bab13cbace2
https://github.com/lepture/mistune/releases/tag/v3.2.1 https://github.com/lepture/mistune/releases/tag/v3.2.1