What is CVE-2026-57585?

CVE-2026-57585 is a high-severity vulnerability in Msgpack Messagepack, classified under Use After Free. CVSS score: 7.5/10. Published 2026-06-30.

How severe is CVE-2026-57585?

High severity. CVSS v3 base score is 7.5 out of 10.

Use After Free in Msgpack Messagepack

CVE-2026-57585

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.

Vulnerability class: Use-After-Free

EPSS: 0.003 (20.1th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

Affected products

Msgpack Messagepack
Msgpack Msgpack-python — versions < 1.2.1

Weakness classification (CWE)

CWE-416 — Use After Free

References

security-advisories@github.com (x_refsource_CONFIRM, Mitigation, Vendor Advisory)
security-advisories@github.com (Patch, x_refsource_MISC)

Frequently asked questions

What is CVE-2026-57585?: CVE-2026-57585 is a high-severity vulnerability in Msgpack Messagepack, classified under Use After Free. CVSS score: 7.5/10. Published 2026-06-30.
How severe is CVE-2026-57585?: High severity. CVSS v3 base score is 7.5 out of 10.