{"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":0.30176,"slug":"CVE-2026-54335","body":"## Overview\n\n### Impact\n\nThe `_.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.\n\n**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`.\n\n### Patches\n\nFixed in `@feathersjs/commons@5.0.45`. The fix skips `__proto__`, `constructor`, and `prototype` keys during iteration — the standard remediation used by lodash and others.\n\n### Workarounds\n\nAvoid passing JSON-parsed untrusted input through `commons._.merge`. Freezing `Object.prototype` or validating/sanitizing keys upstream also mitigates.\n\n### Credit\n\nReported responsibly by Andrew Ridings (@ridingsa).\n\n## Affected packages\n\n- `@feathersjs/commons <= 5.0.44`\n\n## Remediation\n\nUpgrade to a patched release:\n\n- `@feathersjs/commons 5.0.45`","depth":"sunlit","depthScore":20,"depthScoreParts":{"impact":20.4,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}