Attack Surface Analysis for jbogard/mediatr

Attack Surface: Unauthorized Handler Execution

1. Unauthorized Handler Execution
- Description: Attackers trigger MediatR handlers with malicious or unexpected input, bypassing intended application logic and authorization.
- How MediatR Contributes: MediatR's core function is to route messages to handlers. This indirection is the direct mechanism enabling this attack if input validation and authorization within the handler are insufficient.
- Example: An application uses a CreateUserCommand handler. A vulnerability allows an attacker to construct and send a CreateUserCommand directly (bypassing API-level validation) with elevated privileges, creating an unauthorized administrator account. MediatR directly executes this command.
- Impact: Unauthorized data creation/modification/deletion, privilege escalation, execution of arbitrary logic.
- Risk Severity: Critical
- Mitigation Strategies:
  - Input Validation: Implement rigorous input validation within each handler. Treat the request object as untrusted. Use validation libraries.
  - Authorization Checks: Perform authorization checks within each handler.
  - Principle of Least Privilege: Ensure handlers have only minimum necessary permissions.
  - Request Object Design: Design request objects to be specific and constrained.

Attack Surface: Malicious Notification Exploitation

2. Malicious Notification Exploitation
- Description: Attackers exploit vulnerabilities in notification handlers or the notification system to intercept messages, execute malicious code, or cause unintended side effects.
- How MediatR Contributes: MediatR's notification system (INotification, INotificationHandler) is the direct mechanism that allows multiple handlers to respond to a single notification. This broadcast nature is the core contributor to the attack surface.
- Example: A notification is published when a user's password changes. A malicious handler (registered via a separate vulnerability, but executed by MediatR) intercepts this notification and sends the new password to an attacker.
- Impact: Data breaches, unauthorized actions, denial of service (if handlers are resource-intensive).
- Risk Severity: High
- Mitigation Strategies:
  - Handler Review: Thoroughly review all notification handlers for vulnerabilities.
  - Limited Handler Responsibilities: Keep notification handlers focused; avoid complex operations.
  - Asynchronous Notifications: Use PublishAsync where appropriate to mitigate DoS.
  - Secure Dependency Injection: Ensure the DI container prevents unauthorized handler registration (this is a prerequisite for MediatR security).
  - Monitoring: Monitor notification processing.

Attack Surface: Pipeline Behavior Bypass

3. Pipeline Behavior Bypass
- Description: Attackers exploit misconfigurations or vulnerabilities in pipeline behaviors to bypass security checks (validation, authorization).
- How MediatR Contributes: MediatR's pipeline behaviors (IPipelineBehavior) are the direct mechanism for implementing cross-cutting concerns. Incorrect ordering or flawed logic within the MediatR pipeline creates the bypass opportunity.
- Example: A validation behavior is placed after a logging behavior in the MediatR pipeline. An attacker sends an invalid request. The logging behavior (executed by MediatR) logs sensitive data before validation fails.
- Impact: Bypassed security checks, data leakage, unauthorized actions.
- Risk Severity: High
- Mitigation Strategies:
  - Correct Behavior Ordering: Ensure validation/authorization behaviors execute first in the pipeline.
  - Robust Exception Handling: Implement proper exception handling in behaviors.
  - Defense in Depth: Handlers should also perform validation/authorization (MediatR's pipeline is a supplement, not a replacement).
  - Testing: Thoroughly test pipeline behavior interactions within MediatR's context.