Comprehensive Analysis of Broken Access Controls: Models, Vulnerabilities, and Best Practices

Abstract

Broken access controls represent a perennially critical vulnerability within modern information systems, consistently featuring among the most significant security risks identified by organizations such as the Open Web Application Security Project (OWASP) [^1]. These vulnerabilities enable unauthorized entities—be they human users, automated scripts, or compromised systems—to circumvent intended security restrictions and execute actions beyond their legitimate permissions. This comprehensive research delves into the intricate architecture of access control mechanisms, providing an in-depth exploration of various established access control models, meticulously identifying prevalent forms of broken access controls, and subsequently proposing a robust framework of best practices for the systematic design, rigorous implementation, and continuous auditing of secure access control mechanisms. By fostering a profound understanding of these foundational principles and practical applications, organizations can significantly bolster their defensive posture, proactively mitigate the substantial risks associated with unauthorized access, and ultimately safeguard the integrity, confidentiality, and availability of their critical assets.

Many thanks to our sponsor Esdebe who helped us prepare this research report.

1. Introduction

Access control stands as an indispensable pillar of information security, serving as the primary mechanism to enforce the principle of least privilege and ensure that only authorized individuals, processes, or systems can interact with specific resources or execute defined operations within a computing environment. This foundational security control is responsible for regulating who can do what to which resources. The failure of these crucial mechanisms gives rise to ‘broken access controls’—a broad category of vulnerabilities where security restrictions are inadvertently or deliberately bypassed, thereby granting users unintended access to data, functionalities, or system configurations. Such breaches can precipitate a cascade of detrimental outcomes, ranging from profound data exfiltration and corruption to complete system compromise and regulatory non-compliance ^2. Consequently, the strategic importance of designing and implementing resilient, error-free access control systems cannot be overstated in the contemporary threat landscape. This report aims to illuminate the multifaceted nature of these vulnerabilities, drawing upon established security models and current industry insights to provide actionable recommendations for enhancing system security.

Historically, access control has evolved from simple discretionary permissions in early operating systems to complex, policy-driven frameworks required by distributed and cloud-native applications. The increasing complexity of modern software architectures, coupled with the rapid development cycles, often introduces subtle flaws in authorization logic that attackers can exploit. These flaws are not merely implementation bugs but often stem from fundamental misunderstandings of access control principles or inadequate security testing throughout the software development lifecycle ^3. The persistent presence of broken access controls in security assessments underscores the critical need for a more comprehensive and systematic approach to their prevention and remediation.

Many thanks to our sponsor Esdebe who helped us prepare this research report.

2. Access Control Models and Their Evolution

Access control models provide the conceptual and architectural blueprints for defining, enforcing, and managing access policies within information systems. The selection and proper implementation of an appropriate model are paramount to establishing effective security. Each model possesses distinct characteristics, advantages, and limitations, making some more suitable for particular organizational contexts or security requirements than others.

2.1 Discretionary Access Control (DAC)

Discretionary Access Control (DAC) is one of the oldest and most flexible access control models, widely implemented in operating systems and file systems. In DAC, the owner of a resource (or an administrator) has the discretion to grant or revoke access to that resource for other users. This model is characterized by its decentralized nature, where access decisions are typically made by individual users based on their ownership rights [^4].

• Core Principle: Resource owners determine access rights.
• Mechanism: Access Control Lists (ACLs) or capabilities are commonly used. ACLs specify which users or groups have what permissions (read, write, execute) on a given resource. Capabilities are unforgeable tokens that grant specific rights to the holder.
• Advantages: High flexibility, ease of implementation in simple environments, and direct control for resource owners.
• Disadvantages: Can be challenging to manage in large, complex environments due to the decentralized nature of decision-making. It is also susceptible to the ‘Trojan Horse problem,’ where a malicious program operating under a user’s authority can grant unauthorized access to other users ^5. DAC policies can become inconsistent and difficult to audit, potentially leading to unintended access pathways.

2.2 Mandatory Access Control (MAC)

Mandatory Access Control (MAC) is a highly restrictive access control model designed for environments requiring stringent confidentiality and integrity, such as military, government, or high-security commercial systems. Unlike DAC, access decisions in MAC are not at the discretion of the resource owner but are determined by system-wide security policies enforced by a central authority. Both subjects (users, processes) and objects (files, databases) are assigned security labels, and access is granted only if the subject’s label dominates the object’s label according to a predefined hierarchy [^6].

• Core Principle: System-wide policy enforced by a central authority, independent of resource owners.
• Mechanism: Security labels (e.g., ‘Top Secret,’ ‘Secret,’ ‘Confidential,’ ‘Unclassified’) are assigned to both subjects and objects. Access is granted based on the Bell-LaPadula model for confidentiality (no read-up, no write-down) or the Biba model for integrity (no read-down, no write-up) [^6].
• Advantages: Provides a very high level of security, particularly for confidentiality and integrity. Policies are consistent and cannot be overridden by individual users, making it resistant to the Trojan Horse problem.
• Disadvantages: Low flexibility, complex to implement and manage, high administrative overhead, and can be overly restrictive for many commercial applications. Applications need to be specifically designed to operate within a MAC framework.

2.3 Role-Based Access Control (RBAC)

Role-Based Access Control (RBAC) is arguably the most widely adopted access control model in enterprise environments due to its balance of security, flexibility, and manageability. RBAC simplifies permission management by assigning permissions to roles, and then users are assigned to roles based on their job functions or responsibilities within an organization. This decouples user identities from specific permissions, streamlining administration [^7].

• Core Principle: Permissions are associated with roles, and users acquire permissions by being assigned to roles.
• Mechanism: Involves three primary entities: users, roles, and permissions. Roles are collections of permissions required to perform specific job functions. Users can be assigned multiple roles, and roles can have multiple permissions. Hierarchical RBAC extends this by allowing roles to inherit permissions from other roles (e.g., an ‘Administrator’ role might inherit all permissions of a ‘User’ role) ^8. Constrained RBAC adds concepts like separation of duties to prevent a single user from holding conflicting roles.
• Advantages: Simplifies user administration, improves security by centralizing permission management, supports the principle of least privilege, and aligns well with organizational structures. It is highly scalable and adaptable to evolving business requirements.
• Disadvantages: Can become complex to manage in very large organizations with a multitude of granular roles or in dynamic environments where roles change frequently. ‘Role explosion’ can occur if roles are not carefully defined, leading to a system as complex as managing individual permissions.

2.4 Attribute-Based Access Control (ABAC)

Attribute-Based Access Control (ABAC) represents a more dynamic and fine-grained approach, granting access based on a combination of attributes associated with the user (subject), the resource (object), the action being requested, and the environment in which the request is made. ABAC policies are typically expressed as a set of rules that evaluate these attributes at the time of an access request [^9].

• Core Principle: Access is granted based on the evaluation of attributes associated with the subject, object, action, and environment.
• Mechanism: Attributes can include user attributes (e.g., department, clearance level, location), resource attributes (e.g., classification, owner, creation date), action attributes (e.g., read, write, delete), and environmental attributes (e.g., time of day, IP address, device type). Policies are often defined using languages like XACML (eXtensible Access Control Markup Language).
• Advantages: Extremely flexible and dynamic, capable of handling complex access requirements, provides fine-grained authorization, and supports context-aware access decisions. It scales well with the addition of new attributes without requiring changes to existing roles or permissions.
• Disadvantages: Significant complexity in policy definition and management, high computational overhead for evaluating policies at runtime, and requires robust attribute management infrastructure. Debugging and auditing complex ABAC policies can be challenging ^10.

2.5 Lattice-Based Access Control (LBAC)

Lattice-Based Access Control (LBAC) is a model closely related to MAC, primarily used in environments demanding strict data classification and confidentiality. It formalizes the concept of security levels and categories into a mathematical lattice structure, where each subject and object is assigned a security label, and access decisions are made based on the dominance relationship between these labels [^11].

• Core Principle: Access is determined by a formal lattice structure representing security levels and categories.
• Mechanism: Security labels are pairs consisting of a security level (e.g., ‘Secret’) and a set of compartments or categories (e.g., {‘Project Alpha’, ‘Financial Data’}). One label dominates another if its level is greater than or equal to the other’s, and its set of categories includes all categories of the other. Access rules (e.g., a subject can read an object only if its label dominates the object’s label) are strictly enforced.
• Advantages: Mathematically proven security properties, robust enforcement of multi-level security, and strong guarantees against information flow violations.
• Disadvantages: Extremely rigid, complex to implement, and not suitable for general-purpose commercial applications due to its lack of flexibility and significant administrative burden.

2.6 Organization-Based Access Control (OrBAC)

Organization-Based Access Control (OrBAC) offers a high-level, abstract approach to access control, focusing on the organizational structure and its principles rather than low-level technical details. It defines access control in terms of organizations, roles, activities, and views, aiming to bridge the gap between security policies and business requirements [^12].

• Core Principle: Access control policies are derived from organizational structure and business goals.
• Mechanism: Uses concepts like organization (a group of entities with a common goal), roles (functions within an organization), activities (tasks performed), and views (abstract representations of resources). It provides a more semantic and policy-centric view of access control, allowing for easier reasoning about policies in a business context.
• Advantages: Provides a high level of abstraction, making it easier for non-technical stakeholders to understand and define policies. Facilitates policy management and evolution by linking them directly to organizational changes.
• Disadvantages: Requires a robust translation layer to map high-level OrBAC policies into executable low-level access control mechanisms. Can be challenging to implement in existing systems not designed with such a model in mind.

2.7 Relationship-Based Access Control (ReBAC)

Relationship-Based Access Control (ReBAC) models access control decisions based on the relationships between users and resources, often leveraging social graphs or organizational hierarchies. This model is particularly relevant for modern applications where access often depends on how entities are connected ^13.

• Core Principle: Access is granted or denied based on the established relationships between a subject and an object.
• Mechanism: Relationships can be direct (e.g., ‘is owner of’, ‘is manager of’) or indirect (e.g., ‘is a friend of a friend of’). These relationships are often represented in a graph database, allowing for complex queries to determine access. For example, a user might be able to view a document if they are ‘part of the same project team as the document owner’ or ‘an approved external collaborator’.
• Advantages: Highly intuitive for many modern applications, especially social platforms or collaborative tools. Offers fine-grained control and can adapt to dynamic changes in relationships without explicit policy rewrites for every new user or resource.
• Disadvantages: The complexity of defining and querying relationships can be significant. Performance can be a concern for very large and complex relationship graphs. Requires robust graph database or similar infrastructure.

Many thanks to our sponsor Esdebe who helped us prepare this research report.

3. Common Types of Broken Access Controls

Broken access controls manifest in a diverse array of forms, each presenting distinct security risks that attackers exploit to gain unauthorized access or manipulate system behavior. These vulnerabilities are frequently a result of flawed authorization logic, inadequate validation, or incorrect security configurations. Understanding these common types is paramount for developers and security professionals to effectively identify and remediate them.

3.1 Insecure Direct Object References (IDOR)

Insecure Direct Object References (IDORs) occur when an application exposes a direct reference to an internal implementation object, such as a file, database key, or directory, and fails to adequately verify that the user is authorized to access the specified object. Attackers can often bypass authorization checks by merely altering the value of a parameter that directly references an object [^1].

• Mechanism: Instead of using an obfuscated or indirect reference, the application directly uses user-supplied input (e.g., a numeric ID, a filename, a UUID) to retrieve a resource. If the application does not perform an authorization check against the currently logged-in user to confirm their right to access that specific object, an IDOR exists.
• Examples:
  • Changing a URL parameter like https://example.com/account?id=123 to https://example.com/account?id=124 to view another user’s account details.
  • Modifying a hidden form field document_id in a request to access an unauthorized document.
  • Accessing files by guessing their names or sequential identifiers: https://example.com/download?file=invoice_1.pdf changed to invoice_2.pdf.
  • Directly accessing a backend API endpoint by incrementing a user ID in the request body.
• Impact: Unauthorized viewing, modification, or deletion of sensitive user data, intellectual property, or critical system files. Can lead to horizontal or even vertical privilege escalation if the referenced object is an administrative configuration.

3.2 Vertical Privilege Escalation

Vertical privilege escalation occurs when a user with limited privileges gains access to functionalities or data intended for users with higher privilege levels. This allows an attacker to perform actions that should only be available to administrators or other elevated roles ^2.

• Mechanism: Attackers discover hidden administrative functions, manipulate request parameters (e.g., changing a ‘user’ role parameter to ‘admin’), exploit misconfigured access controls on specific API endpoints, or find vulnerabilities in system configuration that grant them elevated permissions. This often involves bypassing checks performed on the client-side or exploiting insufficient checks on the server-side logic.
• Examples:
  • A regular user changing their account type from ‘basic’ to ‘premium’ or ‘admin’ by intercepting and modifying an HTTP request.
  • Accessing an administrative dashboard URL directly (/admin/dashboard) which should be protected, without proper server-side role validation.
  • Exploiting a vulnerability in a file upload function to upload a web shell, gaining server-side code execution with higher privileges.
  • A regular user being able to create, modify, or delete other users’ accounts, including administrative accounts.
• Impact: Complete system compromise, unauthorized data modification or deletion, administrative control over the application, and potential for further lateral movement within the network.

3.3 Horizontal Privilege Escalation

Horizontal privilege escalation refers to a scenario where a user gains access to data or functionalities at the same privilege level but belonging to another user. This is a violation of user-level isolation, allowing one user to impersonate or access resources of another peer user ^2.

• Mechanism: Similar to IDORs, this often involves manipulating identifiers (user IDs, account numbers, document IDs) in requests. The application fails to enforce proper user boundaries, allowing a user to access resources owned by a different user without explicit authorization.
• Examples:
  • A user viewing another user’s private messages or order history by changing an ID in the URL or request body.
  • One user being able to update another user’s profile information.
  • In a multi-tenant application, a user from one tenant gaining access to the data of another tenant.
• Impact: Violation of privacy, unauthorized data access or modification, and potential for impersonation. In a business context, this could lead to competitive espionage or customer data breaches.

3.4 Unprotected or Obscured Endpoints

This vulnerability arises when developers mistakenly rely on ‘security by obscurity,’ attempting to protect sensitive functionalities or data by making their access points difficult to discover, rather than implementing robust authorization checks. Such endpoints might have obscure URLs, be referenced only in client-side JavaScript, or not be linked from the main user interface ^2.

• Mechanism: Attackers do not need to guess obscure URLs. They can discover them through various means, including:
  • Automated scanning tools: Directory enumeration and web content discovery tools can often find hidden paths.
  • Client-side code analysis: Examining JavaScript files, configuration files, or network requests made by the application can reveal hidden API endpoints or administrative pages.
  • API documentation: Publicly exposed or leaked API documentation might reveal sensitive endpoints.
  • Source code disclosure: Inadvertent exposure of application source code.
• Examples:
  • An API endpoint /api/v1/admin_panel_config that is not linked anywhere but can be accessed by an unauthenticated user.
  • A debugging endpoint /dev/status that reveals sensitive system information.
  • A hidden API endpoint for deleting user accounts, only accessible via a POST request from specific pages, but without server-side authorization checks.
• Impact: Depending on the sensitivity of the endpoint, this can lead to information disclosure, unauthorized actions, or complete compromise of the system if administrative functions are exposed.

3.5 Broken Function Level Access Control

This type of vulnerability occurs when an application fails to enforce proper authorization checks at the function level, allowing users to execute privileged functions directly. While a user might not be able to access an administrative page, they might be able to invoke the underlying administrative API function ^14.

• Mechanism: The application might perform access control checks at the UI level (e.g., hiding an ‘Admin’ button) but neglect to implement equivalent server-side checks for the corresponding API endpoint or backend function. Attackers can bypass the UI, often by crafting direct HTTP requests to the unprotected API endpoint.
• Examples:
  • A regular user directly calling an API endpoint like /api/admin/deleteUser with a valid user ID, bypassing any UI-level restrictions.
  • Exploiting a mobile application’s API that does not enforce proper authorization for critical actions, even if the mobile UI restricts them.
• Impact: Unauthorized execution of privileged operations, leading to data loss, service disruption, or system compromise.

3.6 Client-Side Enforced Access Controls

Client-side access controls are a common pitfall where security decisions are made solely on the client (browser, mobile app) without robust server-side validation. This includes disabling buttons, hiding menu items, or relying on JavaScript to enforce permissions [^15].

• Mechanism: Attackers can easily bypass client-side controls by disabling JavaScript, modifying client-side code, or intercepting and modifying network requests using proxy tools. Since the client environment is untrusted, any security logic residing there can be circumvented.
• Examples:
  • An ‘Edit Profile’ button is disabled for non-administrators in the browser, but the underlying PUT /api/user/{id} endpoint allows any authenticated user to modify any profile if there’s no server-side check.
  • JavaScript code checks a user’s role before allowing access to a page, but directly navigating to the page URL bypasses the JavaScript check.
• Impact: Complete bypass of intended access restrictions, leading to horizontal or vertical privilege escalation and arbitrary actions.

3.7 Misconfigured Cross-Origin Resource Sharing (CORS)

While not a direct access control vulnerability in the traditional sense, misconfigured CORS policies can effectively bypass browser-based same-origin policy, allowing unauthorized domains to interact with resources that should be restricted. If an application’s CORS policy is overly permissive, it can expose sensitive data or allow malicious scripts from other domains to perform authenticated requests [^1].

• Mechanism: A web application allows requests from arbitrary origins (e.g., Access-Control-Allow-Origin: *) or reflects the Origin header without proper validation. An attacker can then host a malicious script on their own domain, which makes authenticated requests to the vulnerable application’s domain, effectively bypassing the browser’s security model.
• Examples:
  • A web API that accepts requests from attacker.com due to a permissive Access-Control-Allow-Origin header.
  • A backend service that reflects the Origin header in Access-Control-Allow-Origin, effectively trusting any origin that sends a request.
• Impact: Information disclosure (e.g., an attacker can read sensitive data from the vulnerable domain using JavaScript), cross-site request forgery (CSRF) amplification, and potential for unauthorized actions if the API accepts authenticated requests.

3.8 Improper Handling of Authentication and Session Management

While distinct from access control, flaws in authentication and session management can directly lead to broken access controls. If an attacker can hijack a session, or if sessions are not properly invalidated, they effectively gain the permissions of the legitimate user [^1].

• Mechanism: Weak session token generation (predictable tokens), insecure storage of session tokens (e.g., in URL parameters), lack of session expiration, or failure to invalidate sessions after logout or password changes. Session fixation attacks can also contribute to this.
• Examples:
  • An attacker steals a valid session token (e.g., through XSS or sniffing) and uses it to impersonate the legitimate user indefinitely.
  • A user changes their password, but their old session remains valid, allowing an attacker who possessed the old session token to continue accessing the account.
• Impact: Full account takeover, leading to the same impact as horizontal or vertical privilege escalation depending on the compromised user’s privileges.

Many thanks to our sponsor Esdebe who helped us prepare this research report.

4. Best Practices for Secure Access Control

Implementing robust access control mechanisms requires a systematic approach, integrating security considerations throughout the entire software development lifecycle. Adherence to established best practices is crucial for mitigating common vulnerabilities and building truly resilient systems.

4.1 Principle of Least Privilege (PoLP)

The Principle of Least Privilege (PoLP) is a foundational tenet of information security, dictating that any user, program, or process should be granted only the minimum necessary permissions to perform its intended function, and no more ^16. This principle applies universally, from human users and service accounts to microservices and virtual machines.

• Implementation:
  • Granular Permissions: Instead of broad access, assign specific permissions (e.g., ‘read-only’ instead of ‘all access’).
  • Role Definition: Clearly define roles based on job functions, ensuring each role has only the permissions absolutely required.
  • Temporary Privileges: Implement mechanisms for just-in-time (JIT) access or temporary elevation of privileges for specific tasks, which are automatically revoked after a defined period or task completion.
  • Regular Review: Periodically review and audit assigned privileges to ensure they remain consistent with current job responsibilities and are not excessive.
• Benefits: Reduces the attack surface by limiting the potential damage of a compromised account or system. Prevents unauthorized actions, minimizes the impact of internal threats, and enhances compliance with security regulations.

4.2 Deny by Default (Implicit Deny)

The ‘Deny by Default’ principle, also known as ‘Implicit Deny,’ is a crucial security policy that states that if an access request is not explicitly granted, it must be denied [^17]. This is the inverse of a ‘permit by default’ approach, which is inherently insecure.

• Implementation:
  • Authorization Logic: Design access control systems to default to denial. Only explicitly authorized actions should be permitted. Any new functionality, user, or resource should initially be inaccessible until permissions are explicitly granted.
  • Firewalls and Network ACLs: Configure firewalls and network access control lists to block all traffic by default and only permit specifically defined services or IP addresses.
  • Application-Level Checks: Ensure that all application endpoints and functions are protected by default, requiring specific authorization rules to allow access.
• Benefits: Significantly reduces the risk of accidental exposure of resources. Any misconfiguration or oversight in granting permissions will err on the side of security, ensuring unauthorized access is not inadvertently granted.

4.3 Robust Server-Side Authorization Enforcement

All access control decisions must be enforced on the server-side, as the client-side (web browser, mobile application) is an untrusted environment. Any controls implemented solely on the client can be easily bypassed by a determined attacker [^1].

• Implementation:
  • Centralized Authorization Logic: Implement a centralized authorization module or library on the server that is responsible for all access control decisions.
  • Never Trust Client Input: Always re-validate and re-authorize every request originating from the client, even if client-side logic suggests it should be permitted.
  • API Protection: Ensure that all API endpoints are protected by server-side authorization checks, regardless of whether they are exposed through a user interface.
• Benefits: Guarantees that access controls cannot be bypassed by client-side manipulation, providing a stronger security posture.

4.4 Comprehensive Input Validation and Sanitization

Proper validation and sanitization of all user-supplied input are critical for preventing many types of broken access controls, particularly IDORs and injection-based bypasses [^18].

• Implementation:
  • Whitelist Validation: Validate input against a strict whitelist of expected values, types, and formats (e.g., only allow numeric IDs, specific enumerations, or GUIDs where expected).
  • Canonicalization: Ensure that all input is converted to a standard, unambiguous format before validation and use to prevent path traversal or other canonicalization attacks.
  • Type and Length Checks: Verify that input matches expected data types and falls within acceptable length constraints.
  • Contextual Output Encoding: Encode output based on the context (HTML, URL, JavaScript, SQL) to prevent cross-site scripting (XSS) and other injection attacks that could lead to session hijacking.
• Benefits: Prevents attackers from manipulating application logic by injecting malicious data or directly referencing unauthorized objects, reducing the attack surface for IDORs and other vulnerabilities.

4.5 Secure Session Management

Secure session management is fundamental to preventing unauthorized access by ensuring that authenticated sessions cannot be hijacked or reused by attackers [^1].

• Implementation:
  • Strong Session Token Generation: Use cryptographically strong, unpredictable, and sufficiently long session tokens. Avoid sequential or easily guessable tokens.
  • Secure Transmission: Always transmit session tokens over encrypted channels (HTTPS/TLS) to prevent interception.
  • HttpOnly and Secure Flags: Set the HttpOnly flag on session cookies to prevent client-side scripts from accessing them, mitigating XSS-based session hijacking. Use the Secure flag to ensure cookies are only sent over HTTPS.
  • Strict Session Expiration and Invalidation: Implement appropriate session timeouts (both idle and absolute). Invalidate sessions immediately upon logout, password change, or any suspicious activity. Regenerate session IDs after successful authentication to prevent session fixation attacks.
  • SameSite Attribute: Implement the SameSite cookie attribute (Lax, Strict) to mitigate CSRF attacks by controlling when cookies are sent with cross-site requests.
• Benefits: Protects against session hijacking, session fixation, and replay attacks, ensuring that an authenticated user’s privileges are not abused by unauthorized parties.

4.6 Multi-Factor Authentication (MFA)

Multi-Factor Authentication (MFA) significantly enhances security by requiring users to provide two or more distinct forms of verification before granting access. This adds a crucial layer of defense, making it much harder for attackers to compromise accounts even if they obtain a user’s password ^19.

• Implementation:
  • Combine Factors: Require users to present credentials from different categories (e.g., ‘something you know’ like a password, ‘something you have’ like a security token or phone, ‘something you are’ like a fingerprint).
  • Adaptive MFA: Implement adaptive MFA that dynamically adjusts the authentication requirements based on context (e.g., location, device, time of day, unusual login patterns).
  • Educate Users: Promote and educate users about the importance of MFA and how to use it effectively.
• Benefits: Drastically reduces the risk of credential stuffing, phishing, and brute-force attacks by requiring more than just a compromised password, thereby protecting against unauthorized access even if primary credentials are stolen.

4.7 Regular Auditing and Monitoring

Continuous monitoring and periodic auditing of access controls are essential practices for identifying, responding to, and rectifying vulnerabilities or policy violations in real-time or retrospectively ^20.

• Implementation:
  • Comprehensive Logging: Implement robust logging mechanisms that record all critical security events, including authentication attempts (success/failure), authorization decisions, privilege escalation attempts, changes to access control configurations, and access to sensitive resources.
  • Security Information and Event Management (SIEM): Utilize SIEM systems to aggregate, normalize, and analyze security logs from various sources, enabling correlation of events and detection of suspicious patterns indicative of access control bypasses.
  • Alerting: Configure alerts for anomalous activities, such as repeated failed login attempts, access to resources outside of business hours, or attempts to access administrative functions by non-privileged users.
  • Periodic Access Reviews: Conduct regular reviews of user permissions and role assignments to ensure they remain appropriate and align with the principle of least privilege. Remove stale accounts and unnecessary privileges promptly.
• Benefits: Enables proactive threat detection, facilitates incident response, provides forensic evidence for security investigations, and ensures compliance with regulatory requirements.

4.8 Principle of Separation of Duties (SoD)

Separation of Duties (SoD) is an internal control designed to reduce the risk of fraud, error, and unauthorized actions by distributing critical tasks among multiple individuals, ensuring that no single person has complete control over a process ^21.

• Implementation:
  • Task Decomposition: Break down sensitive processes (e.g., financial transactions, system configuration changes) into distinct sub-tasks.
  • Role Assignments: Assign different roles and corresponding permissions to different individuals for each sub-task, such that no one person can complete the entire process alone. For example, the person who initiates a payment should not be the same person who authorizes its release.
  • Automated Enforcement: Where possible, integrate SoD into workflow systems and access control policies to automatically enforce the separation.
• Benefits: Mitigates insider threats, reduces the risk of fraud and error, improves accountability, and enhances the overall integrity of critical business processes.

4.9 Secure Software Development Lifecycle (SSDLC)

Integrating access control considerations throughout the entire Secure Software Development Lifecycle (SSDLC) is crucial for building secure applications from the ground up, rather than attempting to patch security flaws retrospectively ^3.

• Implementation:
  • Requirements Gathering: Define clear and unambiguous access control requirements early in the design phase.
  • Threat Modeling: Conduct threat modeling exercises to identify potential access control bypasses, privilege escalation vectors, and design flaws before coding begins.
  • Security Architecture Review: Review the application’s architecture to ensure that access control mechanisms are consistently applied and robustly designed.
  • Secure Coding Practices: Train developers on secure coding principles specific to authorization, including robust input validation and server-side enforcement.
  • Security Testing: Incorporate various forms of security testing, including static application security testing (SAST), dynamic application security testing (DAST), penetration testing, and manual code review, specifically targeting access control logic.
  • Deployment and Operations: Ensure secure configuration of access control policies in production environments and monitor their effectiveness continuously.
• Benefits: Reduces the cost and effort of fixing vulnerabilities, improves the overall security posture, and embeds security into the organizational culture.

Many thanks to our sponsor Esdebe who helped us prepare this research report.

5. Conclusion

Broken access controls represent a persistent and often understated threat to the security and integrity of modern information systems. Their pervasive nature, as consistently highlighted by major security frameworks, underscores a fundamental challenge in balancing system functionality with robust security enforcement. This report has meticulously detailed the various conceptual frameworks of access control—from the foundational DAC and MAC to the more adaptable RBAC, ABAC, LBAC, OrBAC, and ReBAC models—demonstrating the evolution of strategies to manage user permissions. Each model offers distinct advantages and trade-offs, making context-aware selection and diligent implementation paramount.

The research further elucidated the common manifestations of broken access controls, including the insidious Insecure Direct Object References (IDORs), the dangerous avenues of vertical and horizontal privilege escalation, the fallacy of security by obscurity, and other critical vulnerabilities such as broken function-level access control, client-side enforcement failures, misconfigured CORS, and inadequate session management. These categories collectively represent the diverse attack vectors that adversaries exploit to bypass intended restrictions and compromise systems.

Crucially, this report has outlined a comprehensive set of best practices essential for constructing and maintaining secure access control mechanisms. These include the fundamental principles of Least Privilege and Deny by Default, the absolute necessity of robust server-side authorization enforcement, meticulous input validation and sanitization, secure session management, the adoption of Multi-Factor Authentication, rigorous auditing and monitoring, the strategic implementation of Separation of Duties, and the integration of security considerations throughout the entire Secure Software Development Lifecycle. By embracing these practices, organizations can move beyond reactive vulnerability patching towards a proactive, resilient security posture.

The ongoing challenge lies in the dynamic nature of modern software development and the increasing complexity of distributed systems. Therefore, continuous vigilance, regular security assessments, and an organizational culture that prioritizes security at every stage are indispensable. Future research could explore advanced machine learning techniques for anomaly detection in access patterns, the standardization of policy definition languages for ABAC, and novel approaches to managing access control in highly decentralized environments such as blockchain-based systems. Ultimately, a deep understanding of access control principles, coupled with their diligent application, remains the most potent defense against the pervasive threat of unauthorized access.

Many thanks to our sponsor Esdebe who helped us prepare this research report.

References

[^1]: OWASP Foundation. (2021). OWASP Top 10 – 2021. Retrieved from https://owasp.org/www-project-top-ten/

[^4]: Saltzer, J. H., & Schroeder, M. D. (1975). The Protection of Information in Computer Systems. Proceedings of the IEEE, 63(9), 1278-1308. Retrieved from https://ieeexplore.ieee.org/document/1458022

[^6]: Bell, D. E., & LaPadula, L. J. (1973). Secure Computer System: Unified Exposition and Multics Interpretation. DTIC Document. Retrieved from https://apps.dtic.mil/sti/pdfs/ADA006551.pdf
[^7]: Ferraiolo, D. F., & Kuhn, D. R. (1992). Role-Based Access Control. 15th National Computer Security Conference. Retrieved from https://csrc.nist.gov/publications/history/ncscl-1992/ncsc-1992-005.pdf

[^9]: Hu, V. C., Kuhn, D. R., & Ferraiolo, D. F. (2014). NIST Special Publication 800-162: Attribute-Based Access Control (ABAC) Definition and Considerations. Retrieved from https://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-162.pdf

[^11]: Denning, D. E. (1976). A Lattice Model of Secure Information Flow. Communications of the ACM, 19(5), 236-243.
[^12]: Ouadjaout, H., Hammal, R., & Djahel, S. (2018). OrBAC-based Access Control Model for Cloud Environment. International Journal of Computer Applications, 179(36), 1-6. Retrieved from https://www.ijcaonline.org/archives/volume179/number36/ouadjaout2018a-id12158.pdf

[^15]: OWASP Foundation. (n.d.). Client-side Security Checklist. Retrieved from https://cheatsheetseries.owasp.org/cheatsheets/Client_Side_Security_Cheat_Sheet.html

[^17]: Puget Sound Hardware. (n.d.). Best Practices For Access Control Systems. Retrieved from https://pugetsoundhardware.com/blogs/news/best-practices-for-access-control-systems
[^18]: OWASP Foundation. (n.d.). Input Validation Cheat Sheet. Retrieved from https://cheatsheetseries.owasp.org/cheatsheets/Input_Validation_Cheat_Sheet.html