Vert.x-web Cross-Site Request Forgery

Vert.x-Web framework v4.0 milestone 1-4 does not perform a correct CSRF verification. Instead of comparing the CSRF token in the request with the CSRF token in the cookie, it compares the CSRF token in the cookie against a CSRF token that is stored in the session. An attacker does not even need to provide a CSRF token in the request because the framework does not consider it. The cookies are automatically sent by the browser and the verification will always succeed, leading to a successful CSRF attack. (2021-01-20, CVE-2020-35217)

The absence of Anti-CSRF tokens may lead to a Cross-Site Request Forgery attack that can result in executing a specific application action as another logged in user, e.g. steal their account by changing their email and password or silently adding a new admin user account when executed from the administrator account.

The attacker may copy one of your web application forms, e.g. email/password change form.

The webpage will contain a form with the exact set of fields as the original application but with input values already provided and the submit button replaced with a Javascript code causing auto-submission. When the page is accessed the form will be immediately submitted and page contents replaced with a valid content or a redirect to your original application.

One of your application users who is already logged in can be then tricked to navigate to such malicious page e.g. by clicking a link in a phishing email, and the pre-populated form content will be submitted to your application like it would be submitted by your user.