Bug 2560108

Summary: CVE-2026-115347 python-mistune: mistune: Denial of Service via unmatched square brackets [fedora-44]
Product: [Fedora] Fedora Reporter: Ronit Dey <rdey>
Component: python-mistuneAssignee: Miro Hrončok <mhroncok>
Status: ON_QA --- QA Contact: Fedora Extras Quality Assurance <extras-qa>
Severity: high Docs Contact:
Priority: high    
Version: 44CC: epel-packagers-sig, mhroncok, neil, python-packagers-sig, romain.geissler
Target Milestone: ---Keywords: Security, SecurityTracking
Target Release: ---   
Hardware: Unspecified   
OS: Unspecified   
Whiteboard: {"flaws": ["65a75d9c-d2bf-452b-ba35-5999f3639a88"]}
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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: 2559327    

Description Ronit Dey 2026-10-23 17:39:35 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 before 3.3.0 contains an inefficient algorithmic complexity vulnerability in parse_link_text that allows remote attackers to cause denial of service through unbalanced square brackets. Attackers can submit markdown containing long runs of unmatched brackets to mistune.html(), triggering repeated forward scans that stall worker processes for minutes.
Comment 1 Fedora Update System 2026-10-28 12:01:57 UTC 
FEDORA-2026-ea39a303cf (python-mistune-3.3.4-1.fc44) has been submitted as an update to Fedora 44.
https://bodhi.fedoraproject.org/updates/FEDORA-2026-ea39a303cf
Comment 2 Fedora Update System 2026-10-29 02:47:21 UTC 
FEDORA-2026-ea39a303cf has been pushed to the Fedora 44 testing repository.
Soon you'll be able to install the update with the following command:
`sudo dnf upgrade --enablerepo=updates-testing --refresh --advisory=FEDORA-2026-ea39a303cf`
You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2026-ea39a303cf

See also https://fedoraproject.org/wiki/QA:Updates_Testing for more information on how to test updates.