TI-2026-42737 Aliases CVE-2026-59929 GHSA-qfrw-5rxm-mhh2

Cross-site scripting in lepture mistune

LOW 27CWE-184Published 2026-07-08 · Updated 2026-07-09

Key facts

Attack vector: Network
Privileges required: None
User interaction: Required
Attack complexity: Low
Impact type: Cross-site scripting
Confidentiality · integrity · availability: Low · Low · None
Fix status: Partial Red Hat: 3 without a fix

Attack profile from CVSS 3.1 · CNA. Fix status from CNA, GitHub and Red Hat. Impact type from CWE-79.

Summary

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV

EPSS 0.00341 27th percentileScored 2026-11-07

Public exploit Yes 1 exploit referenceTagged by NVD

Fix Partial mistune (lepture): 3.3.0mistune (PyPI): 3.3.0Red Hat: 3 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: None
Automatable: No
Technical impact: Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
lepture	mistune	before 3.3.0	3.3.0	Patch available	CNA
—	mistune (PyPI)	before 3.3.0	3.3.0	Patch available	GHSA-qfrw-5rxm-mhh2

mistune Vendorlepture Affected before 3.3.0 Fixed in 3.3.0 Patch available CNA
mistune (PyPI) Vendor— Affected before 3.3.0 Fixed in 3.3.0 Patch available GHSA-qfrw-5rxm-mhh2

CPE configurations NVD · 1

CPE	Versions	Role	Vendor
cpe:2.3:a:mistune_project:mistune::::::::	before 3.3.0	Vulnerable	lepture

cpe:2.3:a:mistune_project:mistune:*:*:*:*:*:*:*:* Versions before 3.3.0 Vulnerable ·lepture

Remediation

Fix · CNA mistune (lepture) Fixed in 3.3.0
Fix · GHSA-qfrw-5rxm-mhh2 mistune (PyPI) Fixed in 3.3.0 Advisory →

Vendor assessments

Red Hat

Red Hat rating: Moderate. Red Hat's page for this CVE →

Product	Status	Plan or fix
Migration Toolkit for Applications 8	Affected	No fix yet: Fix deferred
Red Hat OpenShift AI (RHOAI)	Affected	No fix yet: Fix deferred
Red Hat Satellite 6	Affected	No fix yet: Fix deferred

Timeline

2026-10-02 Threatist record created from CVE-2026-59929
2026-10-03 Alias added: GHSA-qfrw-5rxm-mhh2

References

Other 3

TI-2026-42736 Mistune block_parser: quadratic-time parsing on long lists of repeated reference-link definitions CVSS 3.1HIGH 7.5
TI-2026-42730 Regular expression denial of service in lepture mistune CVSS 3.1HIGH 7.5
TI-2026-42731 Mistune: XSS via percent-encoded javascript URI bypass in safe_url() CVSS 3.1MEDIUM 6.1
TI-2026-32774 Mistune Image Directive CSS Injection Vulnerability CVSS 3.1MEDIUM 6.1
TI-2026-32773 Mistune TOC Anchor Injection XSS CVSS 3.1MEDIUM 6.1
TI-2026-32595 Mistune Math Plugin XSS Escape Bypass CVSS 3.1MEDIUM 6.1

See all 16 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences