Bug 2560106

Summary:	CVE-2026-115347 python-mistune: mistune: Denial of Service via unmatched square brackets [fedora-43]
Product:	[Fedora] Fedora	Reporter:	Ronit Dey <rdey>
Component:	python-mistune	Assignee:	Miro Hrončok <mhroncok>
Status:	CLOSED ERRATA	QA Contact:	Fedora Extras Quality Assurance <extras-qa>
Severity:	high	Docs Contact:
Priority:	high
Version:	43	CC:	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"]}
Fixed In Version:	python-mistune-3.3.4-1.fc43	Doc Type:	---
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2026-11-06 01:51:11 UTC	Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:
Bug Blocks:	2559327

Description Ronit Dey 2026-10-23 17:39:08 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 12:00:21 UTC

FEDORA-2026-340793a2f1 (python-mistune-3.3.4-1.fc43) has been submitted as an update to Fedora 43.
https://bodhi.fedoraproject.org/updates/FEDORA-2026-340793a2f1

Comment 2 Fedora Update System 2026-10-29 02:21:27 UTC

FEDORA-2026-340793a2f1 has been pushed to the Fedora 43 testing repository.
Soon you'll be able to install the update with the following command:
`sudo dnf upgrade --enablerepo=updates-testing --refresh --advisory=FEDORA-2026-340793a2f1`
You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2026-340793a2f1

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

Comment 3 Fedora Update System 2026-11-06 01:51:11 UTC

FEDORA-2026-340793a2f1 (python-mistune-3.3.4-1.fc43) has been pushed to the Fedora 43 stable repository.
If problem still persists, please make note of it in this bug report.