CVE-2026-107299

msgpack5 is a msgpack v5 implementation for node.js and the browser. Prior to 6.1.0, the streaming decoder treats the reserved MessagePack byte 0xc1 as incomplete input instead of invalid input. When 0xc1 begins a stream, subsequent data remains buffered while the decoder waits for bytes that cannot make the value valid, allowing a remote peer to exhaust memory. This issue is fixed in version 6.1.0.

CVSS 3.1

5.9CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS

0.4% chance of exploitation in the next 30 days; higher than 32% of CVEs (scores of 2026-10-25)

CWE

CWE-228

Published

2026-10-08

Modified

2026-10-09

Record from

the NVD, synced 2026-10-19

Packages (OSV)

References

• https://github.com/mcollina/msgpack5/commit/85da345bf1acc18ca441741e5cf4aa0ed0d69314
• https://github.com/mcollina/msgpack5/releases/tag/v6.1.0
• https://github.com/mcollina/msgpack5/security/advisories/GHSA-26wq-p25c-j6fv

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