CRLF Attack

WHAT IS CRLF ATTACK?

A CRLF injection attack, also known as HTTP response splitting, is a type of cyberattack that exploits a vulnerability in web applications. It involves injecting special characters, specifically Carriage Return (CR) and Line Feed (LF), into HTTP headers or other input fields. These characters are used to signify the end of a line in text-based protocols.

HOW DOES CRLF ATTACK WORK?

Input Validation: Reject or sanitize \r\n in user input.

Use Secure HTTP Headers: Properly structure and encode HTTP responses.

Framework Protection: Many modern frameworks (e.g., Express.js, Spring Boot) handle header security automatically.

Escape Logs: Use structured logging to prevent injection attacks.

MITIGATION FOR CRLF ATTACK WORK:

Don’t trust user input: Rework your code so that content supplied by the user is never used directly in the HTTP stream.

Strip newlines: Strip any newline characters before passing content into the HTTP header.

Encode data: Encode the data that you pass into HTTP headers. This will effectively scramble the CR and LF codes if the attacker attempts to inject them.

Escape Logs: Sanitize log data to prevent log injection.

CONCLUSION:

CRLF injection is a serious web security vulnerability that exploits improper input handling to manipulate HTTP headers, logs, or responses. It can lead to HTTP response splitting, XSS, cookie injection, and log manipulation.