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Attack Surface Analysis for vercel/next.js

Attack Surface: Path Traversal in Dynamic Routes

  • Description: Attackers can manipulate URL paths, especially dynamic route parameters, to access files or directories outside the intended web application root.
  • Next.js Contribution: Dynamic routing features in Next.js, particularly when parameters are used to construct file paths on the server (e.g., in getServerSideProps or API routes), directly create opportunities for path traversal if not handled carefully.
  • Example: A route like /api/files/[filename] where filename is directly used to read a file from the server without validation. An attacker could request /api/files/../../../etc/passwd to attempt to read sensitive system files.
  • Impact: Unauthorized access to sensitive files, configuration files, or even application source code.
  • Risk Severity: High
  • Mitigation Strategies:
    • Input Validation and Sanitization: Strictly validate and sanitize all dynamic route parameters before using them in file system operations. Use allowlists of allowed characters or patterns.
    • Absolute Paths: Construct absolute paths to files and directories on the server instead of relying on relative paths derived from user input.
    • Chroot Jails/Sandboxing: In highly sensitive applications, consider using chroot jails or sandboxing techniques to restrict file system access.
    • Principle of Least Privilege: Ensure the application process runs with minimal necessary file system permissions.

Attack Surface: Injection Attacks in API Routes and Data Fetching

  • Description: Attackers inject malicious code (e.g., SQL, command, NoSQL) into application inputs, which are then executed by the server, leading to unauthorized actions or data breaches.
  • Next.js Contribution: API routes and server-side data fetching functions (getServerSideProps, getStaticProps) in Next.js, which are core features for backend logic and data retrieval, directly expose backend functionality and can become vulnerable if inputs are not sanitized.
  • Example: An API route /api/users/[id] that fetches user data from a database using a SQL query constructed directly with the id parameter without sanitization. An attacker could inject SQL code in the id parameter (e.g., 1; DROP TABLE users; --) to manipulate the database.
  • Impact: Data breaches, data manipulation, unauthorized access, denial of service, and potentially remote code execution.
  • Risk Severity: Critical
  • Mitigation Strategies:
    • Parameterized Queries/Prepared Statements: Always use parameterized queries or prepared statements when interacting with databases to prevent SQL injection.
    • Input Validation and Sanitization: Validate and sanitize all user inputs before using them in queries or commands. Use allowlists and escape special characters appropriately for the target system (SQL, shell, etc.).
    • Principle of Least Privilege: Grant database users and application processes only the necessary permissions.

Attack Surface: Server-Side Request Forgery (SSRF) in Data Fetching and Image Optimization

  • Description: Attackers can induce the server to make requests to unintended internal or external resources. This can be used to access internal services, read sensitive data, or perform port scanning.
  • Next.js Contribution: getServerSideProps, getStaticProps, and image optimization features in Next.js, designed for server-side data handling and image processing, can involve making requests to external URLs, directly creating SSRF risks if URLs are not properly validated.
  • Example: An image optimization feature that allows users to provide an image URL. If the application fetches and optimizes the image from the provided URL without validation, an attacker could provide a URL to an internal service (e.g., http://localhost:6379) to interact with it.
  • Impact: Access to internal resources, sensitive data exposure, port scanning, denial of service, and potentially remote code execution in vulnerable internal services.
  • Risk Severity: High
  • Mitigation Strategies:
    • Input Validation and Sanitization (URL Validation): Strictly validate and sanitize URLs provided by users. Use allowlists of allowed domains or protocols.
    • URL Filtering/Blocking: Implement URL filtering or blocking mechanisms to prevent requests to internal networks or sensitive external resources.
    • Network Segmentation: Isolate backend services and restrict network access to only necessary resources.
    • Principle of Least Privilege (Network Access): Ensure the application server has minimal necessary network access.