Improper Authorization via Response Manipulation

---

💰 Estimated Savings: CYVOCATE’s report helped prevent potential financial & reputational losses exceeding $250,000+ due to unauthorized access to restricted functionality.

Introduction

At CYVOCATE, we often uncover subtle authorization flaws that attackers can exploit with simple manipulation techniques.

In this engagement, we identified and exploited a response manipulation vulnerability where client-side trust in HTTP status codes enabled bypassing restricted access. By modifying responses in transit, we gained access to restricted admin functionality, which if left unfixed could have resulted in account takeovers and sensitive data exposure.

Discovery Process

Step 1: Targeting Restricted Resources

The /admin panel returned:

HTTP/2 401 Unauthorized
{"message":"Authentication required"}

This indicated server-side restrictions were in place—but only partially.

Step 2: Response Manipulation

Using Burp Proxy, we intercepted the response and modified:

HTTP/2 401 Unauthorized

to:

HTTP/2 200 OK

Forwarding the manipulated response allowed partial access to the Admin Panel, bypassing the intended authentication flow.

Step 3: Assessing Impact

While not a full compromise, the flaw enabled:

• Loading of restricted admin pages.
• Execution of certain admin functionalities without valid authentication.
• Potential privilege escalation if chained with other weaknesses.

Proof of Concept

• Vulnerability Chain:
  1. Access restricted resource → returns 401 Unauthorized.
  2. Modify response to 200 OK via Burp Proxy.
  3. Application renders admin functionality despite no valid session.
• Impact: Unauthorized access to sensitive features.
• Demonstration: Restricted admin pages loaded in the browser after response tampering.

---

Impact & Risks

• Privilege Escalation: Non-privileged users gaining admin-level visibility.
• Data Exposure: Unauthorized access to sensitive backend endpoints.
• Reputation Loss: Exploitation could compromise trust in access controls.

---

Recommendations

1. Server-Side Authorization Enforcement
   • Validate user roles and session tokens for every request.
   • Never rely on client-side status codes.
2. Session Hardening
   • Implement token-based session validation.
   • Apply strict role-based access control (RBAC).
3. Security Testing Integration
   • Regularly test for bypasses through manual tampering and proxy tools.

---