PT-2026-56519 · Pypi · Mistune

Published 2026-07-08 · Updated 2026-07-08 · CVE-2026-59928

Positive Technologies (AI Summary)

CVSS v3.1

7.5

High

Base vector

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

Name of the Vulnerable Software and Affected Versions Mistune versions prior to 3.3.0

Description A Python Markdown parser with renderers and plugins contains an issue where a Markdown document with numerous repeated or distinct reference-link definitions triggers quadratic work within src/mistune/block parser.py and the ref links environment dictionary handling. This can lead to a denial of service through CPU exhaustion.

Recommendations Update to version 3.3.0.

Exploit

Fix

DoS

Weakness Enumeration

CWE-407

CWE-1333

Related Identifiers

CVE-2026-59928

Affected Products

Mistune

References · 6

• 🔥 https://github.com/lepture/mistune/security/advisories/GHSA-ffq3-xpv3-j92q · Exploit
• https://nvd.nist.gov/vuln/detail/CVE-2026-59928 · Security Note
• https://github.com/lepture/mistune/commit/2b04d7ba341c16ac78fe82d3076bdd5c3de87c69 · Note
• https://github.com/lepture/mistune/releases/tag/v3.3.0 · Note
• https://twitter.com/CVEnew/status/2074931621132652548 · Twitter Post
• https://twitter.com/infoflowcloud/status/2074933043689615544 · Twitter Post