CVE-2026-54335 LOW

CVE-2026-54335: Feathersjs: Prototype pollution in @feathersjs/commons _.merge via JSON-parsed __proto__

Vendor Feathersjs
Product feathers
Weakness CWE-1321
Published July 17, 2026
Last update July 20, 2026

CVSS base score

3.7/10
Attack vector Network
Attack complexity High
Privileges required None
User interaction None
Confidentiality None
Integrity Low

CVSS vector

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N

What the vulnerability does

01Description

Feathersjs is a framework for creating web APIs and real-time applications with TypeScript or JavaScript. In 5.0.44 and earlier, the _.merge(target, source) utility exported by @feathersjs/commons recursively merges source into target by iterating Object.keys(source). When source was produced by JSON.parse and contains a __proto__, constructor, or prototype key, that key is returned as an own-enumerable property; the recursive merge then resolves target['__proto__'] to Object.prototype and writes attacker-supplied properties onto it, polluting the prototype for all plain objects in the process for the lifetime of the Node process. This issue is fixed in version 5.0.45.

Key dates

02Disclosure timeline

July 17, 2026 CVE published
July 20, 2026 Record updated