VulnerabilityDeferred

CVE-2026-107301

msgpack5 is a msgpack v5 implementation for node.js and the browser.

MEDIUM 6.5EPSS 0.37%

Does this matter?

Lower severity and a low EPSS score (0.37%). Track it; it rarely justifies an emergency change on its own.

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.

CVSS 3.1: 6.5 MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:L
EPSS: 0.37% probability · 30th percentile
Public exploits: None in Exploit-DB
CISA KEV: Not listed
Weakness: CWE-1321
Source: security-advisories@github.com

EPSS trend

EPSS moved from 0.4% on 9 October 2026 to 0.4% on 26 October 2026.

References

Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.