attack-tree.md

Attack Tree Analysis for expressjs/express

Objective: To achieve Remote Code Execution (RCE) or Denial of Service (DoS) on the application server specifically by exploiting vulnerabilities or misconfigurations within the Express.js framework itself.

Attack Tree Visualization

                                      Compromise Application (RCE or DoS via Express.js)
                                                      |
                      ---------------------------------------------------------------------------------
                      |                                                                               |
              1. Achieve RCE                                                                 2. Achieve DoS
                      |                                                                               |
      ------------------------------------                                         ------------------------------------                                         
      |                                  |                                         |                                  |
1.1 **Exploit Vulnerable**           1.2 Misuse Express Features                  2.1 Resource Exhaustion          2.2 Exploit Vulnerable
    **Express Version/Deps**             (leading to RCE)                               (via Express)                Express Version/Deps
      |  [HIGH RISK]                         |                                         |                                  |
      ===                                  ===                                       ===                                  ===
      |                                  |                                         |                                  |
   **1.1.2**                            1.2.1 **Prototype**                         **2.1.1**                            **2.2.2**
   **CVE in**                           **Pollution via**                           **High**                             **CVE in**
   **Express**                          **`req.query`,**                            **CPU**                              **Express**
   **Dependency**                       **`req.body`, etc.**                         **Usage**                            **Dependency**
   **(more**                             **(if not**                                 **(e.g.,**                           **(more**
   **common)**                           **properly**                                 **body-**                            **common)**
                                     **sanitized)**                                **parser)**
                                      [HIGH RISK]

Attack Tree Path: 1.1.2 CVE in Express Dependency (RCE)

• Description: An attacker exploits a known vulnerability (CVE - Common Vulnerabilities and Exposures) in a dependency used by the Express.js application. Express itself is a framework and relies on numerous other Node.js packages. These dependencies are frequently updated, and vulnerabilities are often discovered. If the application doesn't keep its dependencies up-to-date, an attacker can leverage a known CVE to gain remote code execution.
• Likelihood: Medium
• Impact: Very High (Complete system compromise)
• Effort: Medium to High
• Skill Level: Intermediate to Advanced
• Detection Difficulty: Medium
• Mitigation:
  • Use npm audit or yarn audit regularly (ideally in CI/CD).
  • Pin dependency versions (package-lock.json or yarn.lock).
  • Vet new dependencies carefully.
  • Use Software Composition Analysis (SCA) tools.
  • Subscribe to security advisories for your dependencies.

Attack Tree Path: 1.2.1 Prototype Pollution via req.query, req.body, etc. (RCE)

• Description: An attacker manipulates user-supplied input (often through query parameters or request bodies) to inject properties into an object's prototype. If the application doesn't properly sanitize this input before using it to construct or modify objects, the attacker can alter the behavior of the application, potentially leading to remote code execution. This is not a vulnerability in Express itself, but a misuse of how Express provides access to request data.
• Likelihood: Medium
• Impact: High to Very High
• Effort: Low to Medium
• Skill Level: Intermediate
• Detection Difficulty: Medium to Hard
• Mitigation:
  • Implement strict input validation and sanitization for all user input.
  • Use a dedicated validation library (Joi, express-validator, validator.js).
  • Avoid directly using user input to construct objects without validation.
  • Be cautious with nested objects and arrays.
  • Consider libraries specifically designed to mitigate prototype pollution.

Attack Tree Path: 2.1.1 High CPU Usage (e.g., body-parser) (DoS)

• Description: An attacker sends specially crafted requests designed to consume excessive CPU resources on the server. A common example is sending very large request bodies or requests with deeply nested JSON structures to middleware like body-parser. If the application doesn't limit the size or complexity of request bodies, the server can become overwhelmed, leading to a denial of service.
• Likelihood: Medium to High
• Impact: Medium to High
• Effort: Very Low
• Skill Level: Beginner
• Detection Difficulty: Easy
• Mitigation:
  • Set reasonable limits on request body sizes using body-parser options (e.g., limit: '100kb').
  • Use rate-limiting middleware (e.g., express-rate-limit).
  • Monitor CPU usage and set up alerts.
  • Consider a Web Application Firewall (WAF).

Attack Tree Path: 2.2.2 CVE in Express Dependency (DoS)

• Description: Similar to 1.1.2, but the exploited vulnerability in the dependency leads to a denial-of-service condition rather than RCE. The attacker might trigger a bug that causes the application to crash, become unresponsive, or consume excessive resources.
• Likelihood: Low to Medium
• Impact: Medium to High
• Effort: Medium to High
• Skill Level: Intermediate to Advanced
• Detection Difficulty: Medium
• Mitigation:
  • Same as 1.1.2 (dependency management is crucial).