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[ CVE-2026-107301 · Published 8 Oct 2026 ]

msgpack5: Partial options disable prototype protection

CVSS 6.5 EPSS <1%Fix available

[ Description ]Official 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.

[ Fixes ]Fixes and patches

  • msgpack5 6.1.0Fixed version · GitHub Advisories · npm package msgpack5: upgrade to 6.1.0 or later (affected < 6.1.0)

[ Packages ]Affected open-source packages

[ References ]References