msgpack5 is a msgpack v5 implementation for node.js and the browser. Prior to 6.1.0, constructing msgpack5 with an empty or partial options object disables the default protoAction: 'error' protection. A decoded map containing a __proto__ key can then replace the decoded object's prototype, potentially changing inherited properties or downstream behavior, although Object.prototype is not modified globally. This issue is fixed in version 6.1.0.
Advisories
Source ID Title
Github GHSA Github GHSA GHSA-8hq7-ggx2-cc6m msgpack5: Partial options disable prototype protection
Fixes

Solution

No solution given by the vendor.


Workaround

No workaround given by the vendor.

History

Thu, 08 Oct 2026 17:15:00 +0000

Type Values Removed Values Added
Description msgpack5 is a msgpack v5 implementation for node.js and the browser. Prior to 6.1.0, constructing msgpack5 with an empty or partial options object disables the default protoAction: 'error' protection. A decoded map containing a __proto__ key can then replace the decoded object's prototype, potentially changing inherited properties or downstream behavior, although Object.prototype is not modified globally. This issue is fixed in version 6.1.0.
Title msgpack5: Partial options disable prototype protection
Weaknesses CWE-1321
References
Metrics cvssV3_1

{'score': 6.5, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:L'}


Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-10-08T17:13:00.613Z

Reserved: 2026-10-07T15:53:23.587Z

Link: CVE-2026-107301

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-10-08T17:17:16.143

Modified: 2026-10-08T17:17:16.143

Link: CVE-2026-107301

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

No data.

Weaknesses