CVE-2026-121437

HighCVSS 7.5/10Last modified Nov 3, 2026

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.

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

Affected software

No affected versions have been published.

Timeline

Published: Nov 3, 2026
Last modified: Nov 3, 2026
NVD status: Deferred

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