| Name | CVE-2026-121437 |
| Description | Mistune from 3.3.0 before 3.3.4 contains a denial of service vulnerability that allows remote attackers to exhaust CPU through quadratic-time emphasis delimiter processing. Attackers can submit small markdown documents with repeated patterns like "*a_b" to trigger an O(n²) index-fixup loop, stalling workers for seconds. |
| 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) |
The table below lists information on source packages.
| Source Package | Release | Version | Status |
|---|---|---|---|
| mistune (PTS) | bookworm | 2.0.4-1 | fixed |
| trixie | 3.1.3-1 | fixed | |
| forky | 3.1.4-1 | vulnerable | |
| sid | 3.4.0-1 | fixed |
The information below is based on the following data on fixed versions.
| Package | Type | Release | Fixed Version | Urgency | Origin | Debian Bugs |
|---|---|---|---|---|---|---|
| mistune | source | bookworm | (not affected) | |||
| mistune | source | trixie | (not affected) | |||
| mistune | source | (unstable) | 3.3.4-1 |
[trixie] - mistune <not-affected> (Vulnerable code not present)
[bookworm] - mistune <not-affected> (Vulnerable code not present)
https://github.com/lepture/mistune/security/advisories/GHSA-qp42-r9j6-83g9
Introduced by: https://github.com/lepture/mistune/commit/5de41fb8e527004dbc363e047a3c380c9288c74f (v3.3.0)
https://github.com/lepture/mistune/commit/b4dd3284e52ec741ed9a227db29ade9017828e90 (v3.3.4)