---
id: CVE-2026-54335
aliases:
  - GHSA-28xv-ph75-77wh
title: Prototype pollution in @feathersjs/commons _.merge via JSON-parsed __proto__
summary: Prototype pollution in @feathersjs/commons _.merge via JSON-parsed __proto__
severity: low
cvss: 3.7
cwe:
  - CWE-1321
vendor: feathersjs
product: '@feathersjs/commons'
ecosystem: npm
affected:
  - '@feathersjs/commons <= 5.0.44'
patched:
  - '@feathersjs/commons 5.0.45'
published: '2026-07-14'
updated: '2026-07-14'
source: GHSA
sourceUrl: 'https://github.com/advisories/GHSA-28xv-ph75-77wh'
references:
  - url: >-
      https://github.com/feathersjs/feathers/security/advisories/GHSA-28xv-ph75-77wh
  - url: 'https://github.com/feathersjs/feathers/pull/3690'
  - url: >-
      https://github.com/feathersjs/feathers/commit/28b3c03c63bdbff53115fdaa46c56980e7942acc
  - url: 'https://github.com/feathersjs/feathers/releases/tag/v5.0.45'
  - url: 'https://github.com/advisories/GHSA-28xv-ph75-77wh'
tags:
  - ghsa
  - npm
ingestedAt: '2026-07-14T20:39:11.399Z'
epss: 0.00389
epssPercentile: 0.32901
---

## Overview

### Impact

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__` (or `constructor` / `prototype`) key, that key is returned as an own-enumerable property. The recursive merge then resolves `target['__proto__']` to `Object.prototype` and writes the attacker-supplied properties onto it, polluting the prototype for all plain objects in the process for the lifetime of the Node process.

**Scope of real-world risk is limited.** No first-party Feathers package routes input — trusted or untrusted — through `commons._.merge`. The `@feathersjs/authentication` package, which does merge request-influenced data, uses `lodash/merge` (prototype-pollution-safe since 4.17.12), not this utility. Exploitation therefore requires a downstream plugin or application to pass JSON-parsed, attacker-controlled input directly through the exported `_.merge`.

### Patches

Fixed in `@feathersjs/commons@5.0.45`. The fix skips `__proto__`, `constructor`, and `prototype` keys during iteration — the standard remediation used by lodash and others.

### Workarounds

Avoid passing JSON-parsed untrusted input through `commons._.merge`. Freezing `Object.prototype` or validating/sanitizing keys upstream also mitigates.

### Credit

Reported responsibly by Andrew Ridings (@ridingsa).

## Affected packages

- `@feathersjs/commons <= 5.0.44`

## Remediation

Upgrade to a patched release:

- `@feathersjs/commons 5.0.45`