Broken Access Control is a type of vulnerability that occurs when a web application fails to properly restrict or enforce user access to certain resources or functionalities. This can allow attackers to access sensitive data, execute unauthorized actions or perform activities reserved only for certain users, such as administrators.

This can happen due to various reasons such as flawed authentication mechanisms, insufficient authorization checks, poorly designed session management, and other issues related to how access control is implemented within the application.

For instance, an attacker might be able to gain access to a restricted area of a website by exploiting a flaw in the authentication process or by bypassing authorization checks. They could also be able to modify or delete sensitive data by exploiting an insufficient access control mechanism.

Broken Access Control bugs can be quite serious as they can lead to significant data breaches, unauthorized access, and other types of malicious activities. Therefore, it is essential for web developers to pay close attention to access control mechanisms when designing and implementing web applications.

How To Test Broken Access Control

Testing for Broken Access Control vulnerabilities requires a combination of manual testing and the use of automated tools. Here are some methods and tools that can be used to test for this type of bug:

1. Manual Testing: Manual testing involves testing the application by attempting to access resources or perform actions that should be restricted. For example, a tester can attempt to access a privileged area of the application without logging in or try to access another user’s account.
2. Fuzzing: Fuzzing is a technique used to test the application by sending random input data to it to try and trigger unexpected behavior. This can help identify vulnerabilities in the application’s access control mechanisms.
3. Security Scanners: There are various security scanners available that can help identify Broken Access Control vulnerabilities in web applications. Some popular tools include Burp Suite, OWASP ZAP, and Nessus.
4. Authorization Testing: Authorization testing involves testing the application’s authorization mechanisms by attempting to perform actions that should be restricted to certain users or roles. For example, a tester can try to access an administrative area of the application with a regular user account.
5. Threat Modeling: Threat modeling is a technique used to identify and prioritize potential threats to an application. By identifying potential threats, testers can design tests that focus on areas of the application that are most likely to be vulnerable to Broken Access Control.

Example of Broken Access Control

Here is a sample request and response that could be indicative of a Broken Access Control vulnerability in a web application:

Request:

POST /admin/delete-user HTTP/1.1
Host: example.com
Content-Type: application/json
Authorization: Bearer eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4gRG9lIiwiaWF0IjoxNTE2MjM5MDIyfQ.SflKxwRJSMeKKF2QT4fwpMeJf36POk6yJV_adQssw5c

{
    "user_id": "123"
}

Response:

HTTP/1.1 200 OK
Content-Type: application/json

{
    "success": true,
    "message": "User deleted successfully"
}

In this example, the request is being made to delete a user with ID 123. The Authorization header contains a bearer token that grants access to this functionality. However, if an unauthorized user were to make a request with a different user ID, they could potentially delete a user that they do not have access to. This is an example of a Broken Access Control vulnerability.

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