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Fencer Intel
high 7.5

CVE-2026-57585 json

MessagePack: Out-of-bounds read/crash on Unpacker reuse after caught error

published 4mo ago modified 17d ago also EUVD-2026-40423 , GHSA-6v7p-g79w-8964 , PYSEC-2026-3625

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 42%
public exploits
0
none known

Summary

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.

Patch / fix

  • pypi msgpack 1.2.1
  • msgpack messagepack 1.2.1
  • python-msgpack Debian 14 1.1.2-3

debian advisories DEBIAN-CVE-2026-57585

  • python-msgpack SLES for SAP 15 SP6, SLES 15 SP6-LTSS, SLE Module for Python 3 15 SP7 1.0.7-150600.3.5.1
  • python-msgpack SLES for SAP 15 SP5, SLES for SAP 15 SP4, SLES 15 SP5-LTSS +5 more 1.0.7-150400.10.9.1
  • python-msgpack Linux Micro 6.1 1.0.5-slfo.1.1_2.1
  • python-msgpack-python Manager Client Tools 12 0.4.6-8.8.1
  • python-msgpack SLES for SAP 15 SP6, SLES for SAP 15 SP5, SLES for SAP 15 SP4 +11 more 0.5.6-150100.3.6.1
  • python-msgpack Linux Micro 6.0 1.0.5-2.1

suse advisories SUSE-SU-2026:4443-1SUSE-SU-2026:3932-1SUSE-SU-2026:23169-1SUSE-SU-2026:3297-1SUSE-SU-2026:3113-1SUSE-SU-2026:22704-1

  • python-msgpack openSUSE Tumbleweed 1.2.1-1.1
  • python-msgpack openSUSE Leap 16.0 1.1.0-160000.3.1

opensuse advisories openSUSE-SU-2026:11586-1openSUSE-SU-2026:21239-1

  • python-msgpack Azure Linux 3.0 1.0.5-3

azure linux advisories AZL-91746

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

Is CVE-2026-57585 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-57585 updated cvss 7.5

msgpack: MessagePack for Python: Denial of Service via Unpacker reuse after error

  • Red Hat Enterprise Linux 9 python-pip, python3-pip, python3.12-pip, python3.14-pip, python3-pip-wheel, python3.12-pip-wheel, +1 more
    affected: workaround, no fix available
  • Red Hat AI Inference Server 3.2 rhaiis/vllm-cuda-rhel9 1790621718, rhaiis/vllm-rocm-rhel9 1790621713
    fixed: vendor fix RHSA-2026:73929
  • Red Hat AI Inference Server 3.4 rhaii/vllm-cpu-rhel9 1790075793, rhaii/vllm-cuda-rhel9 1790090131, rhaii/vllm-rocm-rhel9 1790109620
    fixed: vendor fix RHSA-2026:70965
  • Red Hat Pen Drive Powered by Red Hat Lightspeed pen-drive/pen-drive-scanner-rhel9 Red Hat AI Inference Server rhaii/vllm-tpu-rhel9, rhaiis/vllm-tpu-rhel9, rhaii/vllm-gaudi-rhel9, rhaiis/vllm-spyre-rhel9 Red Hat Ansible Automation Platform 2 automation-controller, ansible-automation-platform-26/hub-rhel9, ansible-automation-platform-27/hub-rhel9, ansible-automation-platform-24/controller-rhel8, ansible-automation-platform-25/controller-rhel8, ansible-automation-platform-26/controller-rhel9, +5 more
    not affected: vulnerable code not present
  • Red Hat Enterprise Linux 8 python3.12-pip, python3.12-pip-wheel
    not affected: vulnerable code not in execute path
  • Red Hat Enterprise Linux 10 python-pip, python-msgpack, python3.14-pip
    not affected: component not present
  • Red Hat Enterprise Linux AI (RHEL AI) 3 rhelai3/bootc-cuda-rhel9, rhelai3/bootc-rocm-rhel9, rhelai3/bootc-gaudi-rhel9, rhelai3/bootc-aws-cuda-rhel9, rhelai3/bootc-gcp-cuda-rhel9, rhelai3/bootc-azure-cuda-rhel9, +1 more Red Hat OpenShift AI (RHOAI) rhai/guidellm-rhel9, rhoai/odh-vllm-gaudi-rhel9, rhoai/odh-kserve-agent-rhel9, rhoai/odh-kserve-router-rhel9, rhoai/odh-feature-server-rhel9, rhoai/odh-kserve-controller-rhel9, +29 more Red Hat OpenShift Container Platform 4 python-msgpack, python3-msgpack, openshift4/ose-ironic-rhel9, openshift4/ose-ironic-agent-rhel9 Red Hat OpenShift Container Platform 5 openshift5/ose-ironic-rhel9, openshift5/ose-ironic-agent-rhel9 Red Hat OpenStack Platform 16.2 python3-msgpack, rhosp-rhel8/openstack-iscsid, rhosp-rhel8/openstack-ec2-api, rhosp-rhel8/openstack-horizon, rhosp-rhel8/openstack-tempest, rhosp-rhel8/openstack-aodh-api, +88 more Red Hat OpenStack Platform 17.1 python3-msgpack
    +3 more products
    Red Hat OpenStack Platform 18.0 python-msgpack, rhoso/openstack-cinder-api-rhel9, rhoso/openstack-glance-api-rhel9, rhoso/openstack-cinder-base-rhel9, rhoso/openstack-manila-share-rhel9, rhoso/openstack-nova-compute-rhel9, +4 more Red Hat Quay 3 quay/quay-rhel8, quay/quay-rhel9 Red Hat Satellite 6 satellite/iop-puptoo-rhel9, satellite/iop-yuptoo-rhel9, satellite/iop-advisor-engine-rhel9, satellite/iop-insights-engine-rhel9
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
4mo ago

Exploit prediction

0.49% chance of exploitation in the next 30 days, higher than 42% of all scored CVEs (FIRST EPSS, 2026-11-11).

CVSS scores

assigned by version score vector
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
GitHub 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
OSV 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected packages

ecosystem package affected fixed in
pypi msgpack
<1.2.1
1.2.1

Affected products

  • msgpack msgpack-python

Classification

Weakness

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

The maintainers of msgpack/msgpack-python published their own advisory on GitHub. Reviewed sources take precedence over it.