Vulnerability record · CVE-2026-59928 · published 8 July 2026

CVE-2026-59928: Mistune project mistune inefficient regular expression (redos) vulnerability

Mistune Project · Mistune

Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, a Markdown document containing many repeated or distinct reference-link definitions causes quadratic work in src/mistune/block_parser.py and the ref_links environment dictionary handling, allowing denial of service through CPU exhaustion. This issue is fixed in version 3.3.0.

7.5 CVSS 3.1 High EPSS 0.65% · top 50.9% CWE-407 · CWE-407CWE-1333 · Inefficient regular expression (ReDoS)

7.5CVSS 3.1 base score

0.65%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

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

Affected products

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

Mistune Mistune Project

References

Link	Tags
https://github.com/lepture/mistune/commit/2b04d7ba341c16ac78fe82d3076bdd5c3de87c69	Patch
https://github.com/lepture/mistune/releases/tag/v3.3.0	Release Notes
https://github.com/lepture/mistune/security/advisories/GHSA-ffq3-xpv3-j92q	ExploitThird Party Advisory
https://github.com/lepture/mistune/security/advisories/GHSA-ffq3-xpv3-j92q	ExploitThird Party 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%8 Jul 2026 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%8 Jul 2026 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%25 Jul 2022 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%8 Jul 2026 6.1CVE-2026-59923Mistune project mistune cross-site scripting vulnerabilityMistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, HTMLRenderer.safe_url() does not block percent-encoded javascript URI…EPSS 0.35%8 Jul 2026 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%26 May 2026 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%26 May 2026 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%26 May 2026

Source: NIST National Vulnerability Database (record CVE-2026-59928), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.