All vulnerabilities
CVE-2026-107297GHSA-gcx5-hxj7-gpqq

msgpack5: Quadratic parsing in the streaming decoder

mcollina msgpack5npmLibraries & packages
Open in ThreatlineRecord JSON
CVSS
5.9Medium
ExploitationNo known exploitationNot in CISA KEV, which does not prove it is unexploitedCISA KEV
Exploit odds (EPSS)0.39%Chance of exploitation activity in the next 30 days, higher than 31% of CVEs. Scored 23 Oct 2026FIRST EPSS
Fixed in6.1.0Fixed versionGitHub
Published8 Oct 2026Updated 8 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

The streaming decoder reparses an incomplete container from the beginning whenever another chunk arrives. A remote peer can split one valid MessagePack value across many small chunks, causing quadratic CPU usage and blocking the event loop.

Patches

The decoder now preserves incremental container state so completed elements are not parsed again when more input arrives.

Workarounds

Buffer each complete MessagePack value before decoding it, or limit the number of chunks accepted for a single value.

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