https://vulnerability.circl.lu/rss/recent/all/10 Most recent entries from all 2026-10-09T14:34:40.451256+00:00 Vulnerability-Lookup info@circl.lu python-feedgen Contains only the most 10 recent entries. https://vulnerability.circl.lu/vuln/fkie_cve-2026-107301 fkie_cve-2026-107301 2026-10-09T14:34:40.482946+00:00

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.

 https://vulnerability.circl.lu/vuln/ghsa-8hq7-ggx2-cc6m GHSA-8hq7-ggx2-cc6m — msgpack5: Partial options disable prototype protection 2026-10-09T14:34:40.483046+00:00

Affected: npm: msgpack5

### Impact

Passing an empty or partial options object disables the default `protoAction: 'error'` protection. A map containing a `__proto__` key can then replace the prototype of the decoded object, potentially changing inherited properties or causing unexpected behavior in downstream code.

Only the decoded object's prototype is affected; this does not modify `Object.prototype` globally.

### Patches

Options are now merged with secure defaults without modifying the caller's object. Unsupported `protoAction` values are rejected.

### Workarounds

Explicitly set `protoAction: 'error'` whenever constructing a msgpack5 instance, and validate decoded values before use.