Bug 2565894 (CVE-2026-121437) - CVE-2026-121437 mistune: mistune: Denial of Service via quadratic-time emphasis delimiter processing
Summary: CVE-2026-121437 mistune: mistune: Denial of Service via quadratic-time emphas...
Keywords:
Status: NEW
Alias: CVE-2026-121437
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
high
high
Target Milestone: ---
Assignee: Product Security
QA Contact:
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2026-11-03 15:40 UTC by OSIDB Bzimport
Modified: 2026-11-04 16:24 UTC (History)
15 users (show)

Fixed In Version:
Clone Of:
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Description OSIDB Bzimport 2026-11-03 15:40:35 UTC 
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.
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