CVE-2026-54335 is a low-severity (CVSS 3.7) CWE-1321 vulnerability in @feathersjs/commons. A fix is available for @feathersjs/commons — see the affected versions and patch details below.
Feathersjs: Prototype pollution in @feathersjs/commons _.merge via JSON-parsed __proto__
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-54335.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2026-54335 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 385,738 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
@feathersjs/commonsnpmDescription
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/[email protected]. 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
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | @feathersjs/commons | all versions | 5.0.45npm install @feathersjs/commons@5.0.45 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @feathersjs/commons, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update @feathersjs/commons to 5.0.45 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-54335 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
Frequently Asked Questions
Is CVE-2026-54335 in your dependencies?
Find it across npm, including transitive dependencies.