10 day with Me | OWASP Top 10 | Day -1: Broken Access Control

The OWASP (Open Web Application Security Project) Top 10 is a widely recognized standard that highlights the most critical security risks for web applications. In the 2021 version, Broken Access Control is identified as the top security threat, emphasizing its prevalence and the severe risks it poses to applications and their users. Let’s explore what broken access control entails, how attackers exploit it, and how developers can mitigate it.

What Is Broken Access Control?

Broken access control occurs when applications fail to enforce proper restrictions on authenticated users. This vulnerability allows attackers to act beyond their intended permissions, such as accessing unauthorized resources, modifying sensitive data, or performing administrative actions.

Access control vulnerabilities can take many forms, including:

1. Vertical Privilege Escalation: A lower-privileged user gains access to higher-privileged functions or data.
2. Horizontal Privilege Escalation: A user accesses resources or data belonging to another user with the same privilege level.
3. Unprotected APIs: Exposed endpoints that allow unauthorized access due to improper checks.
4. Direct Object References (IDOR): Exploiting predictable or exposed object identifiers to access unauthorized resources.

How Does Broken Access Control Work?

Attackers exploit broken access control by identifying and bypassing insufficient permission checks. For example:

Scenario: An application uses user IDs in a URL to fetch sensitive data:

GET /account/12345

If the application doesn’t verify the requester’s ownership of 12345, an attacker could manipulate the URL to access another user’s account:

GET /account/67890

Without proper access control checks, this request could return unauthorized data.

Consequences of Broken Access Control

The impact of broken access control can be catastrophic, including:

• Data Breaches: Unauthorized access to sensitive user or organizational data.
• Service Disruption: Abuse of administrative functionalities to disrupt operations.
• Fraud: Unauthorized financial transactions or manipulation of data.
• Reputation Damage: Loss of customer trust and potential regulatory penalties.

Prevention and Mitigation Strategies

Preventing broken access control requires rigorous attention to access policies and implementation. Here are some key strategies:

1. Enforce Principle of Least Privilege: Ensure users only have access to resources necessary for their role.
2. Role-Based Access Control (RBAC): Implement RBAC to define permissions clearly and prevent over-privileged accounts.
3. Deny by Default: Configure systems to deny access to all resources unless explicitly permitted.
4. Implement Access Control at the Server: Perform access control checks server-side to prevent tampering by malicious clients.
5. Use Secure Object References: Avoid exposing predictable or easily manipulated identifiers for resources.
6. Test for Access Control Weaknesses: Perform regular security assessments and penetration testing to identify vulnerabilities.
7. Audit Logs: Maintain detailed logs of access attempts and monitor them for suspicious activities.

Real-World Examples

1. Uber (2019): Attackers exploited a vulnerability to access sensitive trip and user information due to inadequate access control mechanisms.
2. Facebook (2021): An IDOR vulnerability allowed attackers to view private data by manipulating object identifiers.

Broken access control is a critical threat that underscores the importance of implementing robust and comprehensive access management strategies. By prioritizing secure coding practices, regularly testing for vulnerabilities, and adhering to the principle of least privilege, developers can effectively mitigate this risk. Safeguarding applications against broken access control isn’t just about preventing breaches; it’s about protecting user trust and maintaining the integrity of digital systems.