CVE-2026-107301
msgpack5: Partial options disable prototype protection
CVSS Score
6.5
EPSS Score
0.0%
EPSS Percentile
0th
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.
| CWE | CWE-1321 |
| Vendor | mcollina |
| Product | msgpack5 |
| Published | Oct 8, 2026 |
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CVSS v3 Breakdown
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:L Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
Low
Affected Versions
mcollina / msgpack5
< 6.1.0