VulnerabilityAnalyzed
CVE-2026-59923
Prior to 3.3.0, HTMLRenderer.safe_url() does not block percent-encoded javascript URIs, allowing attacker-supplied Markdown links or images to bypass URL protections and execute script in rendered HTML.
MEDIUM 6.1EPSS 0.35%
Does this matter?
Lower severity and a low EPSS score (0.35%). Track it; it rarely justifies an emergency change on its own.
Description
Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, HTMLRenderer.safe_url() does not block percent-encoded javascript URIs, allowing attacker-supplied Markdown links or images to bypass URL protections and execute script in rendered HTML. This issue is fixed in version 3.3.0.
- CVSS 3.1
- 6.1 MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
- EPSS
- 0.35% probability · 28th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-79
- Affected
- mistune project/mistune
- Source
- security-advisories@github.com
References
- https://github.com/lepture/mistune/commit/c7101fcbb6e8790e8e39157c5ca2238fc6dd6cbcPatch
- https://github.com/lepture/mistune/releases/tag/v3.3.0Release Notes
- https://github.com/lepture/mistune/security/advisories/GHSA-8c25-4j27-2rv3Exploit, Vendor Advisory
- https://github.com/lepture/mistune/security/advisories/GHSA-8c25-4j27-2rv3Exploit, Vendor Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.