Medium 5.9Published Oct 8, 2026

CVE-2026-107299msgpack5: Reserved byte can cause unbounded stream buffering

Updated under an hour ago (2026-10-19 10:00 UTC)

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Every CVE for mcollina msgpack5

Exploited in the last 30 days

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: 5.9 MEDIUM (v3.1, CNA)CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness (CWE): CWE-228
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: GitHub_M
NVD analysis: Deferred
Record last updated: Oct 9, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

mcollina msgpack5 mcollina:msgpack5 (from the name)	before 6.1.0	CNA record

References

https://github.com/mcollina/msgpack5/security/advisories/GHSA-26wq-p25c-j6fvx-refsource-confirm
https://github.com/mcollina/msgpack5/commit/85da345bf1acc18ca441741e5cf4aa0ed0d69314x-refsource-misc
https://github.com/mcollina/msgpack5/releases/tag/v6.1.0x-refsource-misc

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.