Prototype pollution in @feathersjs/commons _.merge via JSON-parsed __proto__

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

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

EPSS

• CVE-2026-54335: 0.39% estimated exploitation activity in the next 30 days; percentile 33.07 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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…

Published by the source

14 Jul 2026, 19:40 UTC

Last modified by the source

14 Jul 2026, 19:56 UTC

Source last checked

26 Oct 2026, 12:56 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-28xv-ph75-77wh

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-28xv-ph75-77wh

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# Patch Next advisory brief: CVE-2026-54335

Advisory: Prototype pollution in @feathersjs/commons _.merge via JSON-parsed __proto__
IDs: CVE-2026-54335, GHSA-28xv-ph75-77wh
Record: https://patchnext.com/advisories/cve-2026-54335 (revision 2, source checked 26 Oct 2026, 12:56 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Low (CVSS 3.7)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: @feathersjs/commons 5.0.45. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm @feathersjs/commons: affected <= 5.0.44; fixed in 5.0.45

## Suggested inspection (read-only)
- `npm ls @feathersjs/commons --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on @feathersjs/commons.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-28xv-ph75-77wh (OSV record GHSA-28xv-ph75-77wh lists affected ranges: npm @feathersjs/commons >=0 <5.0.45 (fixed))
- Verified: https://github.com/advisories/GHSA-28xv-ph75-77wh (GitHub-reviewed advisory GHSA-28xv-ph75-77wh lists affected ranges: npm @feathersjs/commons >=0 <=5.0.44)

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