CVE-2026-57585: MessagePack: Out-of-bounds read/crash on Unpacker reuse after caught error

highCVSS 7.5CVE-2026-57585

CSIRTS triage

vendor: MessagePack product: MessagePack Memory corruption

What: An out-of-bounds read/crash occurs on Unpacker reuse after an error is caught.
Who is affected: Deployments using MessagePack for data unpacking are affected.
Urgency: Remediation is urgent due to high severity and potential for exploitation.
Action: Update to the latest version of MessagePack to mitigate this vulnerability.

AI-assisted analysis generated from the source advisory — verify against the original.

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Details

Source: Microsoft Security Response Center (INTL · vendor-psirt · site)
Severity: high — CVSS 7.5
Published: 2026-06-09
Exploitation: Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-57585

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Low exploitation riskCVE-2026-575850.28% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 20% of all scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-57585	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

highCVE-2026-57585: MessagePack is the serializer implementation for Python msgpack.org. Prior to 1.2.1, there is …nvd

Recent advisories for MessagePack

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

highCVE-2026-57585: MessagePack is the serializer implementation for Python msgpack.org. Prior to 1.2.1, there is …nvd · 2026-06-30