Rate Limit Bypass in Password Reset Functionality

Rate limiting is a crucial security measure that prevents excessive requests from a single user or IP address. However, improper implementation can lead to bypasses, allowing attackers to exploit the system. In this blog post I will discuss how I found a way to bypass rate limit using an X-Forwarded-For header, in a password reset functionality.

Vulnerability Details

The issue lies in how the application handles rate limits for password reset requests. By manipulating the X-Forwarded-For header, an attacker can trick the server into treating each request as coming from a different IP, effectively bypassing any imposed limits.

Steps to Reproduce:

Visit the target website.Go to the login page and click on “Reset Password.”Enter the victim’s email address.Fire-up burp-suite and intercept the request.Add the header X-Forwarded-For:127.0.0.1.

6. Add injection point on last digit of added ip.
(X-Forwarded-For:127.0.0.$1$).

7. Use Burp Suite’s intruder tool:

Set the payload type as numbers.Choose a range (e.g., 1 to 100).

8. Start the attack.

9. The victim will receive a flood of password reset emails.

Impact

This vulnerability enables email bombing, where users receive a large number of password reset emails, causing inconvenience and potential business reputation damage. Additionally, it could be leveraged for social engineering or denial-of-service attacks against specific users.

Conclusion

Rate limiting is essential for application security, but improper implementation can leave systems vulnerable to abuse. Security teams should ensure robust protections are in place to prevent such exploits and protect users from spam attacks.