msgpack5: Reserved byte can cause unbounded stream buffering

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-107299
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-08 17:17:15 UTC
Updated2026-10-08 20:48:36 UTC
Descriptionmsgpack5 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.

Risk And Classification

Primary CVSS: v3.1 5.9 MEDIUM from [email protected]

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

Problem Types: CWE-228 | CWE-228 CWE-228: Improper Handling of Syntactically Invalid Structure

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary5.9MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
3.1CNADECLARED5.9MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Mcollina Msgpack5 affected < 6.1.0 Not specified

References

ReferenceSourceLinkTags
github.com/mcollina/msgpack5/commit/85da345bf1acc18ca441741e5cf4aa0ed0d6... [email protected] github.com
github.com/mcollina/msgpack5/releases/tag/v6.1.0 [email protected] github.com
github.com/mcollina/msgpack5/security/advisories/GHSA-26wq-p25c-j6fv [email protected] github.com
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