From Reset to Takeover: The Exploitation Potential of IDOR in Password Recovery Systems

In the world of penetration testing, it’s often the less obvious areas that harbor the most dangerous vulnerabilities. During a recent engagement, I was tasked with testing the authentication mechanisms of an application. This task is foundational in cybersecurity since the strength of an application’s authentication directly correlates with the overall security of user accounts. A single flaw in this area can open the door to serious breaches.

Initial Exploration: Assessing the Login Mechanism

My approach began as it usually does — with a detailed examination of the login process. I tested for common weaknesses: repeated failed login attempts to trigger account lockout, assessment of password policies, and verification of the CAPTCHA system to guard against automated attacks. Everything seemed solid at first glance. However, experience has taught me that the real danger often lies beneath the surface, hidden in plain sight within the less scrutinized parts of the application.

Forgot Password Page

Exploitation: Manipulating the Forgot Password Feature

This was the case with the “Forgot Password” functionality. On the surface, it appeared to be a straightforward feature: the user enters a registered email address, receives an OTP via email, verifies it, and then is prompted to enter a new password. Simple, right? But in cybersecurity, simplicity can sometimes mask significant vulnerabilities.

After verifying that the login mechanism was well-defended, I turned my attention to the password reset process. My first step was to examine the HTTP requests generated during the “Forgot Password” workflow using Burp Suite. I tried injecting various payloads into the JSON parameters, testing for SQL injection, and modifying headers — common methods that occasionally yield results. But the application held firm against these attacks.

Undeterred, I continued probing. The key moment came when I decided to manipulate the final request that was sent to the server during the password reset process. After receiving and verifying the OTP, I intercepted the request to change the password. This request contained the `email` and `password` parameters, which seemed straightforward enough. However, I wondered what would happen if I changed the `email` parameter to that of a different user account.

To test this theory, I quickly created two accounts using disposable email addresses. I initiated the “Forgot Password” process for the first account and intercepted the request just before submitting the new password. Then, I modified the `email` parameter to the email address of the second account — the target or “victim” account — and forwarded the request to the server.

Bypassing MFA: Exploiting OTP Vulnerabilities

To my surprise and concern, the server accepted the request without any additional verification. The password for the second account was changed successfully. This was a textbook example of an Insecure Direct Object Reference (IDOR), where the application fails to properly authorize the user before allowing access to or modification of another user’s data. This vulnerability alone was serious, but the situation became even more concerning when I considered the potential for full account takeover.

Having changed the victim’s password, I attempted to log into their account. As expected, the application required a 6-digit OTP to verify the account before granting access. This was a final safeguard — the Multi-Factor Authentication (MFA) step. At first glance, this seemed like a robust barrier. But the question remained: could it be bypassed?

I knew that OTPs are typically designed to be difficult to bypass. However, if the application lacked proper rate limiting on the OTP verification step, it could be vulnerable to brute force attacks. With 1,000,000 possible 6-digit combinations, a brute force attack would take some time, but it was feasible with the right tools.

I set up Burp Suite’s Intruder tool to iterate through every possible OTP combination. It was a long shot, but the potential payoff made it worth the effort. As the attack progressed, I carefully monitored the server’s responses. Finally, after approximately 20 minutes, Burp Suite returned a 200 OK response, indicating that I had successfully guessed the correct OTP.

With the OTP in hand, I was able to bypass the MFA step entirely and gain full access to the victim’s account. This demonstrated a complete compromise — from modifying the password to overcoming the final security measure, all due to the combination of an IDOR vulnerability and the absence of rate limiting on the OTP verification process.

Vulnerabilities in Conjunction:

Insecure Direct Object Reference (IDOR) in the Password Reset Process: The ability to change the `email` parameter allowed unauthorized modification of another user’s password.Lack of Rate Limiting on OTP Verification: The absence of rate limiting enabled brute-forcing the OTP, leading to a full account takeover.

Results: A Complete Account Compromise

The success of this attack highlights the critical importance of implementing layered security measures throughout the authentication process. Individually, each vulnerability posed a significant risk, but together, they created a path for a devastating breach.

By exploiting these vulnerabilities in conjunction, I demonstrated how seemingly isolated weaknesses can combine to produce severe security flaws. The lesson here is clear: thorough testing and validation at every step of the authentication process are essential to protect user accounts from exploitation.

Conclusion: The Importance of Layered Security

This experience serves as a stark reminder that even the smallest oversight in security can lead to catastrophic results. As cybersecurity professionals, we must remain vigilant, continuously test, and think like attackers to stay ahead of emerging threats.

By securing each aspect of the authentication process — especially those that may seem innocuous — we can better protect user accounts and uphold the integrity of the applications we safeguard.

Thank you for your attention. I look forward to sharing more insights in future articles!

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