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Vulnerability record · CVE-2026-57585 · published 30 June 2026

CVE-2026-57585: Msgpack messagepack use after free vulnerability

Msgpack · Messagepack

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.

7.5 CVSS 3.1 High EPSS 0.49% · top 60.5% CWE-416 · Use after free
7.5CVSS 3.1 base score
0.49%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
2References
6 Aug 2026Last modified by NVD

Description

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.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/msgpack/msgpack-python/commit/2c56ddb5d0025ed481d962c0f5d62d19dec7476d Patch
https://github.com/msgpack/msgpack-python/security/advisories/GHSA-6v7p-g79w-8964 MitigationVendor Advisory

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Source: NIST National Vulnerability Database (record CVE-2026-57585), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.