How it was found

I would like to report privilege escalation in the npm module express-cart.

It allows a normal user to add another user with administrator privileges.

Module

module name: express-cart version: 1.1.5 npm page: https://www.npmjs.com/package/express-cart

Module Description

expressCart is a fully functional shopping cart built in Node.js (Express, MongoDB) with Stripe, PayPal and Authorize.net payments.

Module Stats

[10] weekly downloads

Vulnerability

Vulnerability Description

A deficiency in the access control allows normal users from expressCart to add new users to the application. This behavior by itself might be considered a privilege escalation. However, it was also possible to add the user as administrator.

Steps To Reproduce:

Firstly, I noticed that all the endpoints located in the user.js file are not being restricted by the common.restrict middleware, as the other admin routes do. Also, the endpoint /admin/user/insert does not check if the user is admin before adding a new user, which I guess it would be a unlikely behavior.

The following code is used to check if it is the first time creating a user:

// set the account to admin if using the setup form. Eg: First user account
let urlParts = url.parse(req.header('Referer'));

let isAdmin = false;
if(urlParts.path === '/admin/setup'){
  isAdmin = true;
}

As you can see in the above snippet, if you send a request with a Referer containing the string /admin/setup the user added will be considered an admin. For example:

POST /admin/user/insert HTTP/1.1
Host: localhost:1111
Referer: http://localhost:1111/admin/setup
Content-Type: application/x-www-form-urlencoded
Cookie: connect.sid=[NORMAL_USER_COOKIE]

usersName=NEWADMIN&[email protected]&userPassword=password&frm_userPassword_confirm=password

Wrap up

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

Impact

This vulnerability would allow any registered user to create another user with administrator privileges and takeover the application.