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.

No CVSS v4.0

Attack Vector Network

Attack Complexity Low

Privileges Required None

Scope Changed

Confidentiality Impact Low

Integrity Impact Low

Availability Impact None

User Interaction Required

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

The EPSS score is 0.00225.

Exploitation none

Automatable no

Technical Impact partial

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions
lepture mistune affected
Version Status Constraints
< 3.3.0 affected —

No data.

No data.

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Advisories
Source ID Title
Github GHSA Github GHSA GHSA-qfrw-5rxm-mhh2 Mistune renderers/html.safe_url: HARMFUL_PROTOCOLS list misses legacy and chained schemes that historically chain to `javascript:` execution
Fixes

Solution

No solution given by the vendor.

Workaround

No workaround given by the vendor.

References
Link Providers
https://github.com/lepture/mistune/commit/c7101fcbb6e8790e8e39157c5ca2238fc6dd6cbc cve-icon cve-icon
https://github.com/lepture/mistune/releases/tag/v3.3.0 cve-icon cve-icon
https://github.com/lepture/mistune/security/advisories/GHSA-qfrw-5rxm-mhh2 cve-icon cve-icon
https://nvd.nist.gov/vuln/detail/CVE-2026-59929 cve-icon
https://www.cve.org/CVERecord?id=CVE-2026-59929 cve-icon
History

Sat, 11 Jul 2026 00:15:00 +0000

Type Values Removed Values Added
References
Metrics threat_severity

None

 threat_severity

Moderate

Thu, 09 Jul 2026 15:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Wed, 08 Jul 2026 17:45:00 +0000

Type Values Removed Values Added
First Time appeared Lepture
Lepture mistune
Vendors & Products Lepture
Lepture mistune

Wed, 08 Jul 2026 16:30:00 +0000

Type Values Removed Values Added
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.
Title Mistune renderers/html.safe_url: HARMFUL_PROTOCOLS list misses legacy and chained schemes that historically chain to `javascript:` execution
Weaknesses CWE-184
CWE-79
References
Metrics cvssV3_1

{'score': 6.1, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N'}

Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-07-09T14:41:36.793Z

Reserved: 2026-07-07T18:20:06.126Z

Link: CVE-2026-59929

cve-icon Vulnrichment

Updated: 2026-07-09T14:21:09.948Z

cve-icon NVD

No data.

cve-icon Redhat

Severity : Moderate

Publid Date: 2026-07-08T16:20:38Z

Links: CVE-2026-59929 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-07-26T17:30:17Z

Weaknesses