CVE-2026-59929 | Mistune is a Python Markdown parser with renderers and plugi… | CVSS 6.1 MEDIUM

Description

Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, the safe_url filter in src/mistune/renderers/html.py blocks only javascript:, vbscript:, file:, and data: schemes, allowing legacy or chained schemes such as feed:, view-source:, jar:, livescript:, mocha:, ms-its:, mk:, and res: to reach rendered href and src attributes and potentially execute script in affected user agents. This issue is fixed in version 3.3.0.

Metadata

CVE ID: CVE-2026-59929
State: PUBLISHED
Assigner: GitHub_M
Reserved: 2026-07-07 18:20 UTC
Published: 2026-07-08 16:20 UTC
Last updated: 2026-07-09 14:41 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

6.1 MEDIUM CVSS 3.1

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

SSVC — CISA Coordinator

Exploitation: none
Automatable: no
Tech. Impact: partial

Affected products (1)

Vendor	Product	Platform	Versions
lepture	mistune	—	< 3.3.0

Weakness (CWE)

CWE	Source	Description
CWE-184	cna	CWE-184: Incomplete List of Disallowed Inputs
CWE-79	cna	CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

CVSS scores (1)

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

References (3)

https://github.com/lepture/mistune/security/advisories/GHSA-qfrw-5rxm-mhh2 https://github.com/lepture/mistune/security/advisories/GHSA-qfrw-5rxm-mhh2
https://github.com/lepture/mistune/commit/c7101fcbb6e8790e8e39157c5ca2238fc6dd6cbc https://github.com/lepture/mistune/commit/c7101fcbb6e8790e8e39157c5ca2238fc6dd6cbc
https://github.com/lepture/mistune/releases/tag/v3.3.0 https://github.com/lepture/mistune/releases/tag/v3.3.0