Exploiting Server-Side Parameter Pollution in a REST URL

Understanding and Mitigating Vulnerabilities in Modern Web Applications

Server-side parameter pollution (SSPP) is a significant yet often overlooked vulnerability in web applications. By manipulating parameters within a REST URL, attackers can exploit this vulnerability to bypass security controls, access unauthorized data, or execute malicious commands. This article delves into the intricacies of SSPP, its potential impact, and best practices for mitigation.

What is Server-Side Parameter Pollution?

Server-side parameter pollution occurs when an attacker manipulates query parameters sent to a server, leading to unexpected behavior in web applications. This can happen when an application processes multiple instances of the same parameter without proper validation or sanitization.

Example Scenario

Consider a RESTful API endpoint that processes user information:

https://example.com/api/user?role=admin&role=user

If the server does not handle duplicate parameters correctly, it might process the request in an unintended manner, potentially granting unauthorized access or exposing sensitive information.