Authorization Bypass

Description

Authorization Bypass is a security flaw in which an application fails to properly enforce permissions, allowing attackers to access resources or perform actions they should not be permitted to. It typically stems from weak or incomplete access control logic. Even though a user may not be authenticated with the correct privileges, they can bypass certain checks (such as direct link guessing, parameter manipulation, or improper session validation) to reach restricted areas or execute restricted functions. In some cases, developers assume client-side or partial checks are sufficient, leaving server-side routes or endpoints unprotected.

Authorization Bypass can have serious consequences, including unauthorized data access, privilege escalation, tampering with sensitive records, or performing administrative actions that compromise the entire application.

Examples

Direct URL Access

An application has administrative pages only meant for admin roles, for instance:

https://example.com/admin/dashboard

If the server does not verify the user's role when they request the /admin/dashboard path, a non-admin user (or even an unauthenticated visitor) might access it directly by entering the URL in a browser.

Parameter Manipulation

Suppose a request includes a parameter specifying the user role or account type:

 POST /updateUser
 Role: user

If the application accepts a modified request such as:

 POST /updateUser
 Role: admin

without verifying the user's actual permissions on the server side, an attacker could escalate privileges and gain administrator-level capabilities.

Skipping Steps in Multi-Step Processes

Some workflows (e.g., e-commerce checkout or registration) use sequential steps enforced on the client side (e.g., step=1, step=2). An attacker could jump directly to the final step or a restricted step by altering the URL or parameters, bypassing required checks if the server does not maintain strict, step-by-step session validation.

Remediation

  1. Enforce Robust Access Control

    • Implement comprehensive server-side checks for each resource, function, or endpoint.
    • Define clear role-based or permission-based access policies and verify permissions for every request, not just at login or on the client side.

  2. Prevent Parameter Tampering

    • Never rely on hidden fields, cookies, or client-side scripts as the sole means of determining user privileges.
    • Validate any user input against expected values and confirm that the request matches the privileges assigned to the user's session on the server side.

  3. Secure Routing and Endpoint Protection

    • Restrict direct URL access by mapping endpoints to authorized roles.
    • Use a centralized mechanism for permission checks (e.g., middleware, filters) within your framework so the logic is consistent and cannot be bypassed in individual controllers or routes.

  4. Session Management and Integrity

    • Ensure session tokens map to user permissions on every request.
    • Protect session tokens from theft or replay attacks through secure cookies, HTTP-only flags, and encryption as needed.