Path Traversal

Written By TheDarkMentor

Understanding Path Traversal Vulnerabilities

Path traversal is a security vulnerability that occurs when an application receives user input to access file system objects without properly sanitizing it. This allows attackers to access files and directories that are stored outside the web root folder, potentially leading to sensitive information disclosure or even remote code execution (RCE). We like RCE, fun for us, terrible for the guy that has to fix it.

Conditions for a Successful Path Traversal Attack

For an attacker to successfully exploit a path traversal vulnerability, certain conditions must be met:

1. Lack of Relative Path Checking: If an application does not properly check for relative path sequences (like ../), an attacker can manipulate file paths to access files outside intended directories.

   To be extra clear there are two types of paths A) Absolute paths and B) Relative paths.

   Example of absolute path: /users/yourname/documents/blog

   Example of relative path: /users/yourname/../../

2. Insufficient Input Validation: Applications failing to validate or sanitize user input can be tricked into divulging files that should be restricted, such as system configuration files.

Consequences of Path Traversal

The impact of a path traversal attack can be significant:

• Sensitive Data Exposure: Attackers can read files containing credentials, source code, or private keys, leading to further exploitation

• Data Tampering: In some cases, attackers can write to arbitrary files, which can be used to upload backdoors or execute malicious scripts

Preventing Path Traversal Vulnerabilities

To prevent path traversal attacks, developers should:

• Avoid User Input in File Paths: Whenever possible, do not use user-supplied input to access file system objects. If necessary, use safer methods to achieve the same functionality

• Input Validation: Validate user input against a whitelist of permitted values or ensure it contains only allowed content, such as alphanumeric characters

• Use of Security Controls: Implement security controls that enforce the expected base folder or file extensions to prevent attackers from using traversal sequences to bypass restrictions

Real-World Exploitation

In practice, attackers exploit path traversal vulnerabilities by manipulating input fields, URLs, or any point where the application might handle file paths. For example, an attacker might change a URL parameter from file=profile.jpg to file=../../../../etc/passwd to attempt to read the system's password file and discover users on the system

Conclusion

So… With what you know now path traversal is a critical vulnerability that can lead to severe security breaches and devastating losses. It’s essential for web developers to understand the risks and implement robust security measures to validate and sanitize user input. A web application should be built with security in mind and adherence to best practices in development can mitigate the risks associated with pathing vulnerabilities.

Also… can we take a moment to enjoy the picture to this blog post. The topic was path traversal and I added a picture of maze. C’mon, you know you like. At least I do, so that’s what really matters.