CVE-2026-59928

EUVD-2026-42338
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.
ProviderTypeBase ScoreAtk. VectorAtk. ComplexityPriv. RequiredVector
NISTPrimary
7.5 HIGH
NETWORK
LOW
NONE
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Base Score
CVSS 3.x
EPSS Score
Percentile: 34.66%
Affected Products (NVD)
VendorProductVersion
mistune_projectmistune
𝑥
< 3.3.0
𝑥
= Vulnerable software versions
Debian logo
Debian Releases
Debian Product
Codename
mistune
bookworm
2.0.4-1
fixed
bullseye
0.8.4-4
fixed
forky
vulnerable
sid
vulnerable
trixie
no-dsa
Ubuntu logo
Ubuntu Releases
Ubuntu Product
Codename
mistune
bionic
needs-triage
focal
needs-triage
jammy
needs-triage
noble
needs-triage
questing
ignored
resolute
needs-triage
Azure Linux logo
Azure Linux Releases
Azure Package
Release
python-mistune
Azure Linux 3.0
0:3.3.0-1.azl3
fixed
Common Weakness Enumeration
References
https://github.com/lepture/mistune/commit/2b04d7ba341c16ac78fe82d3076bdd5c3de87c69
https://github.com/lepture/mistune/releases/tag/v3.3.0
https://github.com/lepture/mistune/security/advisories/GHSA-ffq3-xpv3-j92q
https://github.com/lepture/mistune/security/advisories/GHSA-ffq3-xpv3-j92q