Command Injection

👉 Overview

👀 What ?

Command Injection is a type of attack where an attacker can execute arbitrary commands on the host operating system via a vulnerable application. This attack occurs when an application, which allows users to input data without proper validation, includes this unvalidated data in a command that is dynamically generated and executed on the system.

🧐 Why ?

Understanding Command Injection is crucial as it exposes the vulnerable system to high risk. The attacker can gain control over the system, manipulate data, retrieve confidential information, or even disable the system entirely. Therefore, it's vital for both developers and penetration testers to understand this threat for building secure applications and testing their security respectively.

⛏️ How ?

To protect against Command Injection attacks, it is essential to validate and sanitize all user inputs. Avoid using user input directly in system commands. If it's necessary, use secure function calls, and limit the privileges of the application user to execute commands. Regular security audits and penetration testing can further help identify and fix these vulnerabilities.

⏳ When ?

Command Injection attacks have been in practice since the early days of dynamic web development. As more applications started to interact with the underlying system for various functionalities, the risk of Command Injection attacks increased.

⚙️ Technical Explanations

Command Injection attacks leverage the fact that many high-level programming languages (like Python, Ruby, PHP etc.) offer functions to execute system commands. These functions take a string argument, which is meant to be a system command, and execute it. If an application incorporates user input into this string without validation, it creates a possibility for an attacker to inject malicious commands. For example, if an application uses the input to form a shell command: system('ls ' + user_input); Here, an attacker can provide a command like '; rm -rf /' as input, which would delete all files in the system.