Broken Object-Level Authorization (BOLA): Impact, Example, and Prevention

Ofer Hakimi
April 2, 2024
min to read

What Is Broken Object Level Authorization (BOLA)? 

Broken Object Level Authorization (BOLA) is a security flaw in web applications and APIs that allows unauthorized users to access data by manipulating the object ID in the API call. This issue occurs when an application does not properly verify the user's permission for a requested object, leading to unauthorized data exposure, modification, or deletion. 

BOLA is also known as Insecure Direct Object References (IDOR) and poses significant risks to data integrity and privacy. This vulnerability arises from inadequate or missing authorization checks when objects are accessed directly. 

Attackers exploit BOLA by altering object IDs in the request URL or request body to access or manipulate other users' data. This type of attack is particularly dangerous in systems handling sensitive personal, financial, or business information.

The Open Web Application Security Project (OWASP) Top 10 API security risks (2023) ranks BOLA #1, as the most severe API security vulnerability.

Impact of Object Level Authorization Attacks 

Unauthorized Access to Data

Unauthorized access to data via broken object level authorization attacks can have far-reaching consequences for both users and organizations. When attackers exploit BOLA vulnerabilities, they gain access to sensitive information that should be restricted. This can include personal data such as contact details, financial details, and health records, depending on the nature of the application. 

The exposure of such information not only violates the privacy of users but also puts them at risk of identity theft, fraud, and other forms of cybercrime. For organizations, this unauthorized access can lead to loss of customer trust, reputational damage, and legal repercussions if it is found they failed to protect user data adequately.

Unauthorized Actions

BOLA vulnerabilities also enable unauthorized actions, allowing attackers to perform operations they are not entitled to. This could range from altering user profiles, changing account settings, and unauthorized financial transactions to modifying or deleting data. 

Such actions can disrupt the normal operation of the application, lead to data corruption, and enable further exploitation by attackers. For instance, by modifying user roles or permissions, an attacker could elevate their privileges within the system, granting themselves or others access to even more sensitive areas of the application.

Compliance Violations

Compliance violations are a significant consequence of BOLA attacks, as they can result in organizations failing to meet legal and regulatory standards for data protection and privacy. 

Laws such as the General Data Protection Regulation (GDPR) in Europe and the California Consumer Privacy Act (CCPA) in the United States mandate strict guidelines for handling personal data, including ensuring adequate security measures to protect against unauthorized access and modifications. When BOLA vulnerabilities lead to data breaches or unauthorized data manipulation, organizations can face fines, legal actions, and mandatory reporting obligations.

How BOLA Attacks Work 

Attacks that exploit broken object level authorization typically involve the following steps:

1. Identification of the Vulnerability

Attackers begin by identifying APIs or web applications susceptible to BOLA vulnerabilities. This usually involves probing the application to discover endpoints or functionalities that do not properly verify the user’s access rights to an object. Techniques such as fuzzing or manual testing are used to uncover these flaws.

2. Analysis and Enumeration

Following identification, attackers analyze the pattern and structure of object references within the application. This step may involve enumerating IDs or references to map out accessible objects. Through enumeration, attackers gain a better understanding of how object references correlate with the underlying data.

This analysis helps in pinpointing which objects can be targeted and what types of unauthorized requests might be successful. 

3. Crafting Unauthorized Requests

With the knowledge gained from previous steps, attackers craft unauthorized requests aiming to access or manipulate objects without proper authorization. These requests often mimic or modify legitimate requests, including manipulated object identifiers to point to resources the attacker seeks to access or alter.

This step requires a deep understanding of how the application processes requests and validates user access. Successful manipulation can enable attackers to bypass the intended access controls.

4. Accessing or Manipulating Restricted Data

If the unauthorized requests are successful, attackers gain access to or can manipulate restricted data. Depending on the application's nature and the data's sensitivity, this could entail reading confidential information, altering records, or even performing actions on behalf of other users. Attackers can now leverage the identified vulnerability to compromise data integrity or confidentiality.

BOLA Attack Example 

The example below is based on the OWASP API security guide.

Consider an online document storage service. When a user asks for a document to be deleted, the API receives a GraphQL mutation containing the document ID

  "query":"mutation deleteReports($siteId: ID!, $reportKeys: [String]!) {
      deleteReports(reportKeys: $reportKeys)

Without any further authorization check, the system deletes the identified document. This would allow a malicious user to pass the same GraphQL mutation with a different document ID, using it to delete other users’ documents. 

How to Protect Your APIs from BOLA Vulnerabilities 

Luckily, there are several steps you can take to insure effective object level authorization and protect against BOLA attacks.

1. Enforce Robust Authorization Mechanisms

Authorization mechanisms verify user permissions before granting access to any resources. Effective authorization ensures that each request is authenticated and authorized, preventing unauthorized access or manipulation of data. This approach involves defining clear permission structures and continuously validating user rights throughout the application flow.

Adopting Role-Based Access Control (RBAC) or Attribute-Based Access Control (ABAC) can further enhance security. These models grant access based on roles or attributes, ensuring fine-grained control over who can perform what actions. 

2. Use Random Universally Unique Identifiers (UUIDs)

Another method to protect against BOLA is using random UUIDs for object references. Unlike predictable numeric sequences, UUIDs are difficult to guess, reducing the risk of unauthorized access through ID enumeration. 

This strategy adds a layer of security by obfuscating direct references to objects, making it significantly harder for attackers to manipulate object IDs to access unauthorized data. Employing UUIDs necessitates modifying how your application generates and handles object references. Although this may require additional development effort, it offers real security benefits.

3. Implement the Zero Trust Security Model

The zero trust security model operates on the principle that nothing inside or outside the network should be trusted implicitly. Applying this model involves verifying every request's legitimacy, regardless of its origin, before granting access to resources. It can significantly mitigate BOLA risks by ensuring thorough verification and authorization checks for each interaction with your API.

This model requires a comprehensive approach to security, including identity verification, minimum privilege access, and continuous monitoring of user activities. By adopting zero trust, organizations can create a more secure environment, minimizing the potential for BOLA and other security vulnerabilities.

4. Perform Continuous API Security Testing

Continuous API security testing is essential for identifying and addressing BOLA vulnerabilities. Regular automated scans should be incorporated into the development lifecycle to discover and mitigate security flaws early. 

Dynamic application security testing (DAST) tools can identify potential BOLA issues by analyzing how the application handles object level authorization. Maintaining a schedule for regular security assessments ensures that vulnerabilities are caught and remedied promptly.

API Security with Pynt

Pynt's approach to API security emphasizes a 'shift-left' methodology, focusing on early discovery and resolution of vulnerabilities. This proactive stance in the software development life cycle allows for:

  • Early Detection: Identifying API vulnerabilities early in the development process, reducing potential security risks.
  • Leverages functional tests to detect complex business logic scenarios, providing targeted security insights.
  • Seamless Integration: Facilitating easy integration with existing development tools and pipelines, enhancing developer productivity without compromising security.
  • Comprehensive API Discovery: Automated discovery of APIs, ensuring complete visibility from development to production, crucial for identifying shadow APIs and other hidden risks.

These aspects collectively enhance the overall security posture by addressing API vulnerabilities at their inception, rather than as an afterthought.

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