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Unveiling the Web's Achilles' Heel: Broken Object Level Authorization (BOLA)

June 20, 2023
Written by
Vishnu Prasad K

In an era where our lives are increasingly entangled with the digital realm, ensuring the security of our online presence has never been more crucial. Amidst the buzz of sophisticated cyber threats, a seemingly innocuous vulnerability quietly lurks, waiting to be exploited: Broken Object Level Authorization (BOLA). 

Think of BOLA as a small crack in a seemingly sturdy wall, inconspicuous but capable of granting unauthorized access to sensitive data. It may not make headlines like its more notorious counterparts, but BOLA has the potential to compromise user privacy, manipulate crucial resources, and undermine the very foundations of secure systems.

Table of Contents

  1. What is Broken Object Level Authorization (BOLA)?
  2. Why is BOLA #1 on the OWASP TOP 10 List?
  3. How can an attacker exploit BOLA ?
  4. How to detect Broken Object Level Authorization (BOLA)?
  5. How to prevent BOLA vulnerabilities in your APIs?
  6. Building secure code for resilient applications through Effective Training

What is Broken Object Level Authorization (BOLA)?

Broken Object Level Authorization (BOLA), also known as Insecure Direct Object References (IDOR), is a subtle yet potent vulnerability that plagues many web applications. It arises when an application fails to properly validate and enforce authorization controls at the object level, allowing unauthorized users to access and manipulate sensitive data or resources.

To put it simply, BOLA occurs when an attacker finds a way to bypass the intended restrictions and directly target specific objects within the application. This can lead to unauthorized access to confidential information, such as user profiles, private documents, or even administrative functions. Unlike more obvious security vulnerabilities, BOLA operates in the shadows, exploiting flaws in the authorization logic rather than the traditional authentication mechanisms. It often requires a keen eye and careful analysis to detect and mitigate.

Why is BOLA #1 on the OWASP TOP 10 List?

Though the list for 2023 is not yet confirmed, on the OWASP Github site, broken object-level authorization holds the number 1 position, and it’s for a compelling reason: its potential for severe repercussions and widespread impact. To highlight the significance of BOLA, let's examine the notorious 2018 USPS (United States Postal Service) Data Breach.

In the USPS data breach, attackers exploited a BOLA vulnerability within the USPS Informed Visibility (IV) API. By manipulating the API's request parameters, they were able to access confidential information belonging to other users, including names, addresses, email addresses, and account details. This breach not only compromised the privacy of millions of individuals but also undermined their trust in the USPS's ability to protect their sensitive data. The USPS data breach serves as a wake-up call, demonstrating the real-world implications of BOLA vulnerabilities. It exposed the inherent risks associated with inadequate authorization controls, emphasizing the urgent need for organizations to prioritize proper object-level authorization.

BOLA's prominence on the OWASP TOP 10 List stems from its widespread prevalence across web applications. Many organizations unknowingly leave their systems vulnerable to BOLA, underestimating the potential impact it can have on their users and their own reputation. By ranking BOLA as the number one vulnerability, OWASP aims to draw attention to this critical issue and encourage developers and security professionals to proactively address and mitigate BOLA risks.

How can an attacker exploit BOLA ?

An attacker can exploit Broken Object Level Authorization (BOLA) by leveraging vulnerabilities in the authorization mechanisms of a web application. Here are some common methods attackers may employ to exploit BOLA:

1. Direct Object Reference

Direct Object Reference (DOR) is a vulnerability that grants attackers the power to bypass authorization controls and snatch up sensitive information with a flick of their fingers.

With DOR, the game is all about exposing the weaknesses in authorization checks. Attackers tinker with parameters, dance with URLs, and meddle with hidden form fields to trick the system into granting unauthorized access. It's a thrilling exploit that puts sensitive information within their grasp and leaves organizations scrambling to contain the damage.

2. ID Guessing

ID Guessing is a cunning technique employed by attackers to exploit vulnerabilities in web applications, particularly those affected by Broken Object Level Authorization (BOLA). It involves systematically guessing or iterating through object identifiers or parameters to gain unauthorized access to restricted resources or data.

By guessing or iterating through a range of possible IDs, attackers can bypass the intended authorization checks and gain access to unauthorized resources. They exploit the application's failure to adequately validate and enforce proper access controls, opening the door to potential data breaches or unauthorized actions.

3. Insecure Direct Object References

Insecure Direct Object References (IDOR) pose a significant threat to web application security, making them a prime target for attackers looking to exploit vulnerabilities. IDOR occurs when an application exposes internal object references directly to users without proper authorization checks, allowing attackers to manipulate those references and gain unauthorized access to sensitive information.

Insecure Direct Object References provide attackers with a direct pathway to sensitive information, such as personal data, financial records, or confidential documents. By exploiting IDOR vulnerabilities, attackers can bypass security measures and compromise the integrity, confidentiality, and availability of the application's resources.

4. Privilege Escalation

Privilege escalation refers to the unauthorized elevation of privileges that an attacker can achieve by exploiting vulnerabilities in the application's authorization mechanisms. It allows them to gain access to administrative or privileged functionalities, surpassing the limitations imposed on their original user role or permissions.

By manipulating parameters, user profiles, or other authorization mechanisms, attackers can bypass the checks intended to prevent unauthorized access. They might tamper with session tokens, modify user IDs, or exploit other vulnerabilities to masquerade as an authorized user with elevated privileges.

5. Mass Assignment

Mass Assignment occurs when a web application blindly accepts user-supplied input and uses it to update or assign values to object properties without proper validation or authorization checks. This vulnerability can lead to unauthorized modifications to sensitive data or resources.

Attackers exploit the Mass Assignment vulnerability by manipulating or crafting input parameters to modify properties they shouldn't have access to. By submitting additional or unexpected fields, an attacker can attempt to change sensitive attributes or even escalate their privileges within the application.

How to detect Broken Object Level Authorization (BOLA)?

Detecting Broken Object Level Authorization (BOLA) requires a vigilant eye and thorough analysis of the application's authorization mechanisms. While BOLA vulnerabilities can be elusive, there are several indicators and techniques that can help uncover them and strengthen the overall security posture of the application.

  1. Security Assessments. Conduct routine security audits, including vulnerability scanning and penetration testing, to find any potential BOLA flaws.

  1. In-Depth Code Review. Perform a meticulous code review, focusing on the sections of code responsible for authorization and access control.

  1. Contextual Authorization Analysis. Analyze the application's authorization logic to ensure that it considers contextual information when making access control decisions. 

  1. Parameter Tampering and Input Validation. Attempt to manipulate input parameters, such as URLs, form fields, or API requests, to access unauthorized objects.

  1. User Role Mapping. Review the mapping of user roles to their corresponding privileges and access levels.

  1. Access Logs and Monitoring. Implement logging and monitoring mechanisms to track access attempts and detect suspicious activities.

  1. User Testing and Scenario Simulation. Conduct user testing with various roles and permissions to ensure that authorized users may access the proper resources while unauthorized users are effectively denied.

How to prevent BOLA vulnerabilities in your APIs?

Preventing Broken Object Level Authorization (BOLA) vulnerabilities in your APIs requires a proactive approach that focuses on implementing strong authorization controls and ensuring the integrity of access to resources. By following these key practices, you can bolster the security of your APIs and mitigate the risk of BOLA exploits.

  1. Fine-Grained Authorization - Fine-grained authorization is an essential control mechanism for preventing Broken Object Level Authorization (BOLA) vulnerabilities. By explicitly defining and enforcing access control at the object level, fine-grained authorization mitigates the risk of attackers exploiting direct object references or other weaknesses in authorization controls. To implement fine-grained authorization, developers must first identify the objects within their API that require access control and define the attributes or properties that should be used to determine access rights. Then, access control policies and rules should be defined based on these attributes, ensuring that only authorized users or groups can access specific objects or perform specific actions on them.
  1. Contextual Validation - Contextual validation checks that the requested actions or access are within the user's authorized scope by taking into account the context, relationships, and business rules related to the objects being accessed. Contextual validation ensures that access control decisions are not solely based on the identity or role of the user but also take into account additional contextual information. This information may include factors such as the ownership of the object, the current state of the system, the user's previous actions, or any relevant business rules.
  1. Secure Object References - Instead of revealing direct and predictable references, secure object references use indirect or abstracted references to access objects. Direct object references, such as object IDs or URLs that directly represent resources, can be exploited by attackers to bypass authorization checks and access objects they shouldn't have permission for.
  1. Input Validation and Sanitization - Input validation ensures that the data provided by users or external sources conform to expected formats, ranges, and constraints. By validating input, organizations can ensure that only legitimate and properly formatted data is processed by the application. This prevents attackers from manipulating input parameters to exploit vulnerabilities in the authorization process. Sanitization, on the other hand, involves removing or neutralizing potentially harmful or malicious content from user input. It helps prevent code injection attacks, such as SQL injection or cross-site scripting (XSS), by eliminating or escaping special characters and tags that could be used to execute unauthorized actions or compromise the security of the system.
  1. Security Education and Training - By providing comprehensive education and training programs, organizations can foster a security-conscious culture among developers, system administrators, and other personnel involved in the development and maintenance of applications and APIs. AppSecEngineer is one platform that seeks to solve the problems associated with inconsistent and disjointed security training. AppSecEngineer is a comprehensive training platform designed to provide consistent and high-quality security education for all team members. It offers a vast library of world-class application security content, covering various aspects of secure development, secure coding practices, and vulnerability mitigation.

Building secure code for resilient applications through Effective Training

To exploit BOLA successfully, attackers often rely on careful reconnaissance, analyzing the application's behavior, understanding its data structures, and identifying potential weaknesses in the authorization logic. By exploiting BOLA vulnerabilities, attackers can gain unauthorized access to sensitive information, manipulate data, perform unauthorized actions, or even compromise the entire system.

Platforms like AppSecEngineer can be instrumental in providing the necessary resources and training to promote secure coding practices. We offer comprehensive security education and training programs that enable developers and system administrators to understand and mitigate BOLA vulnerabilities effectively.

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…focused on making sure that you have what it takes to build secured products and to NEVER ship a bad line of code again!

Source for article
Vishnu Prasad K

Vishnu Prasad K

Vishnu Prasad is a DevSecOps Lead at we45. A DevSecOps and Security Automation wizard, he has implemented security in DevOps for numerous Fortune 500 companies. Vishnu has experience in Continuous Integration and Continuous Delivery across various verticals, using tools like Jenkins, Selenium, Docker, and other DevOps tools. His role sees him automating SAST, DAST, and SCA security tools at every phase of the build pipeline. He commands knowledge of every major security tool out there, including ZAP, Burp, Findsecbugs, and npm audit, among many others. He's a tireless innovator, having Dockerized his entire security automation process for cross-platform support to build pipelines seamlessly. When AFK, he is either pouring over Investment journals or in the swimming pool.

Vishnu Prasad K


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