Understanding Broken Access Control Vulnerability: A Comprehensive Guide

Broken Access Control is one of the most critical vulnerabilities in web applications, identified by OWASP as a top security risk. This vulnerability arises when an application fails to enforce proper restrictions on authenticated users or systems, allowing unauthorized access to sensitive data, functionalities, or administrative controls.

In this blog, we will explore the concepts, causes, examples, detection methods, mitigation strategies, and real-world impacts of Broken Access Control vulnerabilities.

What is Broken Access Control?

Access control ensures that users or systems can only access resources they are authorized to use. Broken Access Control occurs when these restrictions are improperly implemented, allowing unauthorized users to:

• Access restricted resources.
• Perform unauthorized actions (e.g., modifying or deleting data).
• Gain elevated privileges (privilege escalation).

Key Concepts of Access Control

1. Authentication vs. Authorization
   • Authentication: Verifying the identity of a user (e.g., login credentials).
   • Authorization: Determining whether an authenticated user has permission to perform an action or access a resource.
     Broken Access Control primarily affects the authorization layer.
2. Access Control Types
   • Role-Based Access Control (RBAC): Permissions are assigned based on user roles.
   • Attribute-Based Access Control (ABAC): Permissions are determined by user attributes, context, or environment.
   • Discretionary Access Control (DAC): Users have control over their resources and can assign access permissions.
3. Common Weaknesses
   • Missing access control checks.
   • Improperly enforced restrictions at endpoints.
   • Relying solely on client-side enforcement (e.g., hidden fields or JavaScript).

Examples of Broken Access Control

1. Horizontal Privilege Escalation
   A regular user can access another user’s data by altering parameters.
   • Example: /api/user/12345 is accessible by changing it to /api/user/12346.
2. Vertical Privilege Escalation
   A low-privilege user gains access to administrative functionalities.
   • Example: Accessing /admin/dashboard without proper checks.
3. Directory Traversal
   Manipulating file paths to access restricted directories.
   • Example: ../../etc/passwd.
4. Unprotected APIs
   APIs expose sensitive endpoints without validating user permissions.
   • Example: Directly invoking /deleteUser API without verifying admin privileges.

Real-World Examples

• Facebook (2019): A vulnerability allowed attackers to view private photos of users by manipulating Graph API calls.
• Uber (2016): Attackers accessed driver and rider data by changing the UUIDs in API requests.

Detecting Broken Access Control

1. Manual Testing
   • Test endpoints and APIs with different user roles.
   • Attempt privilege escalation by modifying cookies, tokens, or parameters.
2. Automated Tools
   • Burp Suite: Intercept requests and manipulate parameters to test access control.
   • OWASP ZAP: Perform automated scans to detect misconfigurations.
3. Code Review
   • Identify insecure or missing access control mechanisms in the backend.
4. Penetration Testing
   • Simulate attacks using predefined scenarios to uncover vulnerabilities.

Mitigation Strategies

1. Implement Proper Access Controls
   • Validate user permissions server-side for every request.
   • Use RBAC or ABAC models to structure access.
2. Deny by Default
   • Restrict access to all endpoints by default and explicitly allow access where needed.
3. Use Secure Development Practices
   • Avoid hardcoding credentials or roles in the application.
   • Enforce least privilege principles.
4. Conduct Regular Audits
   • Perform regular vulnerability assessments and penetration tests.
   • Use logging and monitoring to detect unauthorized access attempts.
5. Apply Security Controls in APIs
   • Validate API keys, tokens, and user roles for all API endpoints.
   • Use secure frameworks that provide built-in access control mechanisms.

Role of Penetration Testing in Identifying Broken Access Control

Penetration Testing simulates real-world attacks to uncover vulnerabilities. At bugv, our experts specialize in identifying and reporting Broken Access Control vulnerabilities. We utilize advanced tools and manual techniques to ensure robust security for your applications.

Our approach includes:

• Scanning for exposed endpoints.
• Testing different user roles and permissions.
• Providing detailed reports with actionable fixes.

Conclusion

Broken Access Control is a severe vulnerability that can compromise the confidentiality, integrity, and availability of an application. By understanding its root causes, implementing robust controls, and performing regular security assessments, organizations can mitigate the risks effectively.

At Bugv, we help businesses secure their applications against such vulnerabilities. Stay proactive in your security measures and protect your data from unauthorized access.

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Contact bugv for expert penetration testing and vulnerability assessments.
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