Bug 2544588

Summary:	CVE-2026-57585 python3.13-pip: MessagePack for Python: Denial of Service via Unpacker reuse after error [epel-all]
Product:	[Fedora] Fedora EPEL	Reporter:	Tomas Hoger <thoger>
Component:	python3.13-pip	Assignee:	Python Maintainers <python-maint>
Status:	CLOSED NOTABUG	QA Contact:
Severity:	high	Docs Contact:
Priority:	high
Version:	epel10	CC:	ksurma, mhroncok, python-maint, python-packagers-sig
Target Milestone:	---	Keywords:	Security, SecurityTracking
Target Release:	---
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:	{"flaws": ["49a30b0f-ca41-47e7-b653-d4dcde03b9a6"]}
Fixed In Version:		Doc Type:	---
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2026-10-14 12:31:41 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:	2496020

Description Tomas Hoger 2026-10-01 11:36:06 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.

MessagePack is the serializer implementation for Python msgpack.org. Prior to 1.2.1, there is an Out-of-bounds read/crash on Unpacker reuse after a caught error, potentially leading to a DoS attack.  If the Unpacker is used repeatedly after an error occurs, the process may crash with a SEGV. This issue has been fixed in version 1.2.1.

Comment 1 Miro Hrončok 2026-10-14 12:31:41 UTC

pip vendors msgpack (via CacheControl) as pure-Python only – the C unpack path where CVE-2026-57585 lives (use-after-free in unpack_template.h) is not shipped. Additionally, pip's only msgpack consumer, cachecontrol/serialize.py, calls msgpack.loads() one-shot and never reuses an Unpacker instance, so the reuse-after-caught-error precondition for the flaw cannot occur.