Bug 2568135

Summary: CVE-2026-121437 python-mistune08: mistune: Denial of Service via quadratic-time emphasis delimiter processing [epel-all]
Product: [Fedora] Fedora EPEL Reporter: Ganesh <gnaik>
Component: python-mistune08Assignee: Orphan Owner <extras-orphan>
Status: NEW --- QA Contact:
Severity: high Docs Contact:
Priority: high    
Version: epel10CC: epel-packagers-sig, extras-orphan, neil, python-packagers-sig
Target Milestone: ---Keywords: Security, SecurityTracking
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Hardware: Unspecified   
OS: Unspecified   
Whiteboard: {"flaws": ["7200d086-af76-49ed-a0ba-1a764ab9a5da"]}
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
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Bug Depends On:    
Bug Blocks: 2565894    

Description Ganesh 2026-11-06 14:04:46 UTC 
Disclaimer: Community trackers are created by Red Hat Product Security team on a best effort basis. Package maintainers are required to ascertain if the flaw indeed affects their package, before starting the update process.

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.