All vulnerabilities
CVE-2026-107296GHSA-qw35-55vc-rhgj

msgpack5: Decoding negative int64 values mutates the input buffer

mcollina msgpack5npmLibraries & packages
Open in ThreatlineRecord JSON
CVSS
3.7Low
ExploitationNo known exploitationNot in CISA KEV, which does not prove it is unexploitedCISA KEV
Exploit odds (EPSS)0.28%Chance of exploitation activity in the next 30 days, higher than 18% of CVEs. Scored 23 Oct 2026FIRST EPSS
Fixed in6.1.0Fixed versionGitHub
Published8 Oct 2026Updated 14 Oct 2026CVE List

What fixes it

  • 6.1.0msgpack5, npmGitHubnpm install msgpack5@6.1.0

A fixed version on one release line is not the upgrade target for every line. Check your exact version and any vendor backports.

Description

Impact

Decoding a negative signed 64-bit integer modifies the corresponding bytes in the caller-provided input buffer. Applications that retain or reuse encoded input for integrity checks, logging, or subsequent processing may observe silently corrupted data.

Positive integers and other MessagePack value types are not affected.

Patches

The decoder now computes signed 64-bit values without writing to the input buffer.

Workarounds

Copy untrusted MessagePack input before decoding it, or do not retain or reuse input buffers after decoding.

Text from GitHub Advisory Database

Affected versions 3

  • msgpack5, npm< 6.1.0GitHub
  • msgpack5affected: < 6.1.0CVE List
  • msgpack5, npmfrom first release, fixed in 6.1.0OSV

References 4