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

> Prototype pollution in FeathersJS allows attackers to inject properties into Object.prototype via JSON input, potentially leading to code execution.

- **Severity:** Low 3.7 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 17 Jul 2026
- **Updated:** 20 Jul 2026
- **Also known as:** GHSA-28xv-ph75-77wh

## What is CVE-2026-54335?

CVE-2026-54335 is a low-severity code injection vulnerability in feathersjs feathers, published on 17 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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.

Weakness: CWE-1321 (Improperly Controlled Modification of Object Prototype Attributes)

## Which versions are affected by CVE-2026-54335?

2 open source packages ship an affected version, including @feathersjs/commons.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `@feathersjs/commons` | npm | All versions | 5.0.45 |
| `@feathersjs/commons` | npm | All versions | 5.0.45 |

## How do I fix CVE-2026-54335?

Upgrade @feathersjs/commons to 5.0.45 or later.

## Is CVE-2026-54335 being exploited?

There is no known exploitation of CVE-2026-54335 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-54335 and fix it if it is affected.

What it is: CVE-2026-54335 is a low-severity code injection vulnerability in feathersjs feathers, published on 17 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-54335 in the wild and no public exploit code.

Affected packages and fixed versions:
- @feathersjs/commons (npm): affected all versions; fixed in 5.0.45
- @feathersjs/commons (npm): affected all versions; fixed in 5.0.45

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-54335/ (Markdown: https://insights.sbomify.com/CVE-2026-54335/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-54335
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-54335
- OSV: https://osv.dev/vulnerability/CVE-2026-54335

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-54335/
Summaries are generated and may contain mistakes; the official description above is the record.