Introduction to Broken Object Level Authorization (BOLA)

Quick Summary: Vulnerabilities like Broken Object Level Authorization can put your APIs at a high risk of cyberattacks. Keep reading to learn more about this API vulnerability, which is described as the most critical in the OWASP vulnerability list, and what you can do to prevent it.

Today, APIs are among the most critical attack vectors for organizations. They are ubiquitous and widely used in applications. Since they are widespread in organizations, it makes them a foremost choice for attackers to plan a cyberattack.

Attackers look for API vulnerabilities like Broken Object Level Authorization for a successful attack. It is a type of vulnerability that occurs when an API allows access to objects but doesn’t validate a user’s access to those objects.

With this flaw, an unauthorized user can access other users’ data. Attackers can use it to modify or steal data. It is important to identify and resolve such types of vulnerability to ensure a robust security posture for your environment.

You can discover most API threats using an advanced vulnerability scanner. Such a scanner will thoroughly scan your applications and discover insecure API endpoints. Moreover, let’s learn more about broken object level authorization, how it occurs, and ways to prevent it.

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What is BOLA (Broken Object Level Authorization)?

When APIs allow users to access data objects without verifying whether they are authorized or not, this is termed Broken Object Level Authorization or BOLA vulnerability. It is a critical security vulnerability that sits on top of the OWASP API Top 10 Security Risks list. It is also referred to as IDOR (Insecure Data Object Reference) vulnerability.

Object-level authorization is a kind of security mechanism devised to protect unauthorized access to objects. So, it defines the control mechanism that determines which users can access which type of objects. It is implemented at the code level to ensure that users with the requisite permissions can access specific objects.

Let’s understand it with an example.

Imagine an automobile manufacturer that produces cars that can be remotely controlled with the use of a mobile-based application. There is an API that sits between the user and the car that handles the requests by a user like turning the engine on/off, locking/unlocking car doors, and more.

In this process, the API receives the VIN (Vehicle Identification Number). However, the API fails to validate that the VIN received is related to a car that belongs to the user logged in. It results in the BOLA vulnerability that an attacker can exploit to control others’ cars.

Impact of Broken Object Level Authorization on Your Organization

The Broken Object Level Authorization API vulnerability leads to severe impacts on your organization. It not only puts your sensitive data at risk but also expands your attack surface for a bigger attack. It can also be challenging to cope with a data breach when it happens due to this vulnerability. The best-case scenario would be to perform a vulnerability assessment to find and remediate such security loopholes and avoid data compromises. Let’s see the overall impact of it.

• There is a strong possibility of data exposure when there is a BOLA or IDOR vulnerability. Attackers can easily exploit these vulnerabilities by using scripts. Consequently, your data can be compromised.
• An attacker can manipulate data by editing, delete, modify, or view the data.
• By exploiting this vulnerability, an attacker can even take control over admin accounts.
• An attacker can get privilege escalation providing access to resources that only high-level users can access.
• The incident of a data breach will result in reputational damage. It will be hard to retain existing customers or acquire new ones.
• A data breach will result in compliance issues and attract penalties and legal action.

Types of Broken Object Level Authorization

Broken Object Level Authorization (BOLA) is a vulnerability that takes place when an application improperly implements authorization checks for user-specific objects or resources. Let’s check out its main types.

Insecure Direct Object References (IDOR)

This type of BOLA vulnerability occurs when the exploiter misuses input parameters to access or modify objects they are prohibited to interact with. For example, modifying a URL parameter to access someone else's data.

Missing Authorization Checks

This occurs when a system can’t verify whether a user has the required permissions to access a particular object or resource. This can cause unauthorized access if the authorization logic is not enforced or is bypassed.

Broken Access Control Logic

It involves flawed implementation of access control measures, where systems fail to properly perform permissions or roles for accessing resources. This leads to potential unauthorized access.

Improper Object Filtering

This vulnerability occurs when the system does not correctly filter objects on the basis of user permissions. This increases the chances of unauthorized access misusing objects they should not be accessible to.

How Does a BOLA Attack Unfold?

Any API that allows user inputs is susceptible to BOLA exploits if there is no proper validation for inputs. Because this vulnerability occurs due to improper implementation of data object access controls, as a result, any kind of user, including malicious actors, can access internal objects. They get the ability to perform actions they are not permitted to.

Moreover, attackers try to discover Broken Object Level Authorization flaws by manipulating user or object ID and observing the responses. They identify the vulnerability when the response is not an error. Let’s see what the attack looks like with an example:

Discover the Flaw

An attacker starts by looking for the Broken Object Level Authorization flaw. The attacker examines how application URLs or API endpoints are constructed. When there is a direct reference to objects, it indicates that the target application or API is vulnerable to BOLA attacks.

For example, there is a pseudo API endpoint for a finance application that downloads statement with the following URL:

example.com/statements/download_as_pdf?statement_id=1025

Now an attacker can manipulate the statement_id to access and download the statements for other users.

Let’s see another example of BOLA provided by OWASP. It is regarding an online document storage application that enables users to edit, delete, and store documents. A GraphQL mutation comprising a document ID is forwarded to the API when a user attempts to delete a document. Look at the following code to see the working:

POST /graphql  {  "operationName":"deleteReports",  "variables":{  "reportKeys":["<DOCUMENT\_ID>"]  },  "query":"mutation deleteReports($siteId: ID!, $reportKeys: [String]!) {  {  deleteReports(reportKeys: $reportKeys)  }  }"  }

In this case, the problem occurs when the code enables users to delete documents without checking for requisite permissions. Consequently, a user could accidentally or purposely delete another user’s document.

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Modifying the Object Reference

After finding a potential object reference weakness, aka BOLA vulnerability, the attacker will manipulate the object ID. The ID is the reference to the object that is sent within an API request. The ID can be a sequence of integers or a generic string. The attacker can identify them in the request headers, query string parameters, or path.

Once the object reference is discovered, the attacker can manipulate it. In some cases, it can be as simple as modifying digits or could be complex based on the application logic and URL structure. An attacker can obtain the ID and perform actions on behalf of another user in case requests are not properly authorized.

Data Breach

Eventually, the attacker gains unauthorized access to data by successfully manipulating the reference. There will be dire consequences for the users as the attacker can modify personal information, account settings, make transactions, and do other unethical activities. It results in a data breach and puts user data at risk of theft and manipulation.

Why Discovering BOLA Vulnerability is Important?

Broken Object Level Authorization is a serious security risk that can lead to unauthorized data disclosure, manipulation, and destruction. Failing to implement access control policies properly is the root cause of BOLA security flaws. Finding and fixing it is crucial to API security.

• Restricting unauthorized access: Often, there are different users with different roles. They have restrictions on what they can access. Identifying and remediating object-level authorization flaws enables you to firmly implement role-based access policies and prevent unauthorized access.
• Avoid data leaks: When confidential data is leaked to an unauthorized party unintentionally, it is known as a data leak. Vulnerabilities like object-level authorization flaws can cause data leaks and expose confidential company information to others. With effective control of data objects, you can ensure your confidential information is not leaked.
• Protect data: Identifying and remediating the BOLA OWASP API risk enables you to effectively protect your data. Attackers steal your data under your nose by exploiting such vulnerability. However, with proper access controls, only users with the requisite permissions can access data, preventing data theft.
• Meet compliance requirements: Organizations need to implement proper security controls to protect users’ data under HIPAA, GDPR, and other such regulations. Discovering and resolving API vulnerabilities can help you prevent data breaches and comply with regulations.

How to Prevent and Mitigate Risks from BOLA Vulnerability?

The following are some tips to help you prevent and mitigate the risks arising from insecure data object references.

Follow Best Practices

Following the API security best practices help you avoid security flaws and protect your data from the bottom. For example, you should use random object reference IDs that are hard to guess to not to leave a clue for attackers. Further, keep track of objects that users can access and check every request for the requisite access privileges.

Authentication and Session Management

By implementing authentication and session management, you can strongly avoid cybersecurity risks. Authenticate users for every session and manage sessions properly. For example, invalidate a session after a specific time of inactivity. The user should be reauthenticated in the next session.

Ensure Proper Access Controls

Make sure that access controls are implemented properly to allow only authorized access to data. Here, authorization is crucial for every data access request. You can leverage role-based access controls and implement them properly to restrict users from accessing what they are not allowed to.

Implement Rate Limiting

Rate limiting restricts the number of requests an API can handle over a certain period. As a result, it prevents attackers from overloading the API with excessive traffic. It ensures an API’s performance and stability.

API Security Testing

You can identify different types of vulnerabilities in APIs by performing rigorous security testing. It helps you uncover the threat landscape and take the necessary steps to mitigate these risks. With API security testing, you can identify vulnerabilities and fix them before they get you into trouble.

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