CVE-2026-107301

msgpack5: Partial options disable prototype protection

Published Oct 8, 2026 CVSS 3.1 · 6.5 Medium EPSS < 1% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Github GHSA Github GHSA GHSA-8hq7-ggx2-cc6m msgpack5: Partial options disable prototype protection
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
First Time appeared Mcollina
Mcollina msgpack5
Vendors & Products Mcollina
Mcollina msgpack5
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'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
Oct 14, 2026, 1:02 AM
Reserved
Oct 7, 2026, 3:53 PM
Status
Deferred
Published
Oct 8, 2026, 5:17 PM
Modified
Oct 14, 2026, 1:17 AM