CVE-2026-59928

Name	CVE-2026-59928
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.
Source	CVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)

Vulnerable and fixed packages

The table below lists information on source packages.

Source Package	Release	Version	Status
mistune (PTS)	bullseye	0.8.4-4	vulnerable
	bookworm	2.0.4-1	vulnerable
	trixie	3.1.3-1	vulnerable
	forky, sid	3.1.4-1	vulnerable

The information below is based on the following data on fixed versions.

Package	Type	Release	Fixed Version	Urgency	Origin	Debian Bugs
mistune	source	(unstable)	(unfixed)

Notes

https://github.com/lepture/mistune/security/advisories/GHSA-ffq3-xpv3-j92q
Fixed by: https://github.com/lepture/mistune/commit/2b04d7ba341c16ac78fe82d3076bdd5c3de87c69 (v3.3.0)