Skip to content

fix(commons): skip prototype-polluting keys in _.merge #3695

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
marshallswain merged 1 commit into from
Aug 10, 2026
+14 −0
Merged

fix(commons): skip prototype-polluting keys in _.merge #3695

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
fix(commons): skip prototype-polluting keys in _.merge 
Object.keys() returns __proto__ as an own enumerable key for
JSON-parsed sources, causing the recursive merge to write onto
Object.prototype. Skip __proto__/constructor/prototype keys.

Same remediation as dove #3690 / @feathersjs/commons@5.0.45
(GHSA-28xv-ph75-77wh / CVE-2026-54335).

Reported-by: Andrew Ridings (@ridingsa)
  • Loading branch information
@marshallswain
marshallswain committed Aug 10, 2026
commit e6abffce9829893292cf901d0c7902a56cfcd18b
5 changes: 5 additions & 0 deletions packages/commons/src/utils.ts
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -75,6 +75,11 @@ export const _ = {
merge (target: any, source: any) {
if (_.isObject(target) && _.isObject(source)) {
Object.keys(source).forEach(key => {
// Skip prototype-polluting keys (e.g. JSON-parsed `__proto__`)
if (key === '__proto__' || key === 'constructor' || key === 'prototype') {
return;
}

if (_.isObject(source[key])) {
if (!target[key]) {
Object.assign(target, { [key]: {} });
Expand Down
9 changes: 9 additions & 0 deletions packages/commons/test/utils.test.ts
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -167,6 +167,15 @@ describe('@feathersjs/commons utils', () => {

assert.equal(_.merge('hello', {}), 'hello');
});

it('merge does not pollute Object.prototype', () => {
_.merge({}, JSON.parse('{"__proto__":{"polluted":"x"}}'));
_.merge({}, JSON.parse('{"constructor":{"prototype":{"polluted2":"y"}}}'));
assert.strictEqual(({} as any).polluted, undefined);
assert.strictEqual(({} as any).polluted2, undefined);
assert.strictEqual((Object.prototype as any).polluted, undefined);
assert.strictEqual((Object.prototype as any).polluted2, undefined);
});
});

describe('makeUrl', function () {
Expand Down
Loading