Bug 2544589 - CVE-2026-57585 pypy: MessagePack for Python: Denial of Service via Unpacker reuse after error [fedora-all]
Summary: CVE-2026-57585 pypy: MessagePack for Python: Denial of Service via Unpacker r...
Keywords:
Status: CLOSED NOTABUG
Alias: None
Product: Fedora
Classification: Fedora
Component: pypy
Version: rawhide
Hardware: Unspecified
OS: Unspecified
high
high
Target Milestone: ---
Assignee: Python Maintainers
QA Contact: Fedora Extras Quality Assurance
URL:
Whiteboard: {"flaws": ["49a30b0f-ca41-47e7-b653-d...
Depends On:
Blocks: CVE-2026-57585
TreeView+ depends on / blocked
 
Reported: 2026-10-01 11:36 UTC by Tomas Hoger
Modified: 2026-10-14 12:23 UTC (History)
4 users (show)

Fixed In Version:
Clone Of:
Environment:
Last Closed: 2026-10-14 12:23:39 UTC
Type: ---
Embargoed:

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Description Tomas Hoger 2026-10-01 11:36:19 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 12:23:39 UTC 
pypy bundles a pip wheel.

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.
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