High severity · published Jun 30, 2026
CVE-2026-57585
MessagePack: Out-of-bounds read/crash on Unpacker reuse after caught error
7.5
CVSS
0.5%
EPSS
No
On KEV
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 vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
None
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.5% · higher than 42% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
MS
msgpack-python · msgpack
< 1.2.1 · source: vendor
ME
Messagepack · Msgpack
before 1.2.1 · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-57585
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-57585
Patch
https://github.com/msgpack/msgpack-python/commit/2c56ddb5d0025ed481d962c0f5d62d19dec7476d
Mitigation
https://github.com/msgpack/msgpack-python/security/advisories/GHSA-6v7p-g79w-8964
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