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Vulnerability record · CVE-2026-59923 · published 8 July 2026

CVE-2026-59923: Mistune project mistune cross-site scripting vulnerability

Mistune Project · Mistune

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.

6.1 CVSS 3.1 Medium EPSS 0.35% · top 74.2% CWE-79 · Cross-site scripting
6.1CVSS 3.1 base score
0.35%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
4References, 2 tagged exploit
9 Jul 2026Last modified by NVD

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

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/lepture/mistune/commit/c7101fcbb6e8790e8e39157c5ca2238fc6dd6cbc Patch
https://github.com/lepture/mistune/releases/tag/v3.3.0 Release Notes
https://github.com/lepture/mistune/security/advisories/GHSA-8c25-4j27-2rv3 ExploitVendor Advisory
https://github.com/lepture/mistune/security/advisories/GHSA-8c25-4j27-2rv3 ExploitVendor Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

7.5CVE-2026-59925Mistune project mistune inefficient regular expression (redos) vulnerabilityMistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, long sequences of well-formed double-asterisk or triple-asterisk emph…EPSS 0.64%7.5CVE-2026-59928Mistune project mistune inefficient regular expression (redos) vulnerabilityMistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, a Markdown document containing many repeated or distinct reference-li…EPSS 0.65%7.5CVE-2026-59922Mistune project mistune inefficient regular expression (redos) vulnerabilityMistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, a run of closed tilde, equals-sign, or caret marker pairs around a ch…EPSS 0.64%7.5CVE-2022-34749Mistune project mistune inefficient regular expression (redos) vulnerabilityIn mistune through 2.0.2, support of inline markup is implemented by using regular expressions that can involve a high amount of backtracking on cert…EPSS 1.5%6.1CVE-2026-59929Mistune project mistune cross-site scripting vulnerabilityMistune 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 java…EPSS 0.34%6.1CVE-2026-44897Mistune project mistune cross-site scripting vulnerabilityMistune is a Python Markdown parser with renderers and plugins. Prior to 3.2.1, HTMLRenderer.heading() builds the opening <hN> tag by string-concaten…EPSS 0.27%6.1CVE-2026-44898Mistune project mistune cross-site scripting vulnerabilityMistune is a Python Markdown parser with renderers and plugins. Prior to 3.2.1, render_toc_ul() builds a <ul> table-of-contents tree from a list of (…EPSS 0.27%6.1CVE-2026-44899Mistune project mistune cross-site scripting vulnerabilityMistune is a Python Markdown parser with renderers and plugins. Prior to 3.2.1, the Image directive plugin validates the :width: and :height: options…EPSS 0.27%

Source: NIST National Vulnerability Database (record CVE-2026-59923), CISA KEV, FIRST EPSS (scores of 2026-09-28). This page is refreshed as NVD updates the record.