CVE-2026-59928

HighCVSS 7.5/10Last modified Oct 25, 2026

Description

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.

Metrics

CVSS 3.1 7.5/10CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Weakness enumeration

CWE-407 CWE-1333

Affected software

Vendor	Product	Versions
lepture	mistune	< 3.3.0

References

https://github.com/lepture/mistune/commit/2b04d7ba341c16ac78fe82d3076bdd5c3de87c69Patch
https://github.com/lepture/mistune/releases/tag/v3.3.0Release Notes
https://github.com/lepture/mistune/security/advisories/GHSA-ffq3-xpv3-j92qExploit, Third Party Advisory
https://github.com/lepture/mistune/security/advisories/GHSA-ffq3-xpv3-j92qExploit, Third Party Advisory

Timeline

Published: Jul 8, 2026
Last modified: Oct 25, 2026
NVD status: Analyzed

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