Identification of Directory Traversal

Directory Traversal, also known as Path Traversal, is a vulnerability that allows attackers to access files and directories that are stored outside the web root folder. By manipulating variables that reference files with dot-dot-slash (../) sequences and other similar methods, an attacker can access arbitrary files and directories stored on the file system, including application source code, installation scripts, and sensitive configuration files.

1. Identification of Directory Traversal Vulnerabilities

Identification Process:

  • The penetration tester attempts to access files and directories outside the intended web directory by manipulating file paths in the application's input (e.g., URL parameters, form inputs).
  • The tester uses typical traversal sequences like "../" or "%c0%af" (URL-encoded) to navigate the file system in an attempt to retrieve files.
  • The response from the application is analyzed to determine if the traversal attempt was successful, which could indicate the presence of a directory traversal vulnerability.


  • The tester might manipulate a URL parameter that is supposed to specify a file within a directory, such as, changing it to in an attempt to access the Unix password file.

2. Tools and Techniques

  • Manual Testing: Manually altering request parameters or paths in URLs, forms, and cookies to include traversal sequences and observing the application's response.
  • Automated Scanning: Using automated tools and scanners that can identify potential directory traversal vulnerabilities by sending various traversal payloads and analyzing the responses.
  • Code Review: Conducting a thorough code review to identify points where user input is used to access file system resources without proper sanitization.

3. Mitigation Strategies

  • Input Validation: Implement strict input validation to disallow potentially dangerous characters or sequences in file paths. Use allow-lists (formerly known as white-lists) for input validation where possible.
  • Use Secure APIs: Use file access APIs that are designed to eliminate the risk of directory traversal by automatically encoding or filtering potentially dangerous inputs.
  • Least Privilege: Ensure the application runs with the minimum necessary file system permissions to limit the impact of a successful directory traversal attack.

4. Best Practices for Penetration Testers

  • Comprehensive Testing: Test with a variety of traversal sequences, including simple "../" sequences, URL-encoded sequences, and other obfuscations that might bypass weak filters.
  • Document Findings: Clearly document the vulnerability, including how it was discovered, the potential impact, and steps to reproduce the issue.
  • Ethical Conduct: Ensure all testing is authorized and avoid accessing or displaying sensitive data discovered during testing to minimize the risk of data breaches or legal issues.

By effectively identifying and addressing directory traversal vulnerabilities, penetration testers can help organizations protect their systems and data from unauthorized access and potential exploitation.