🚨CRLF Injection: Guide to Finding & Exploiting Vulnerabilities

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Hello, cybersecurity enthusiasts! 👋 In this comprehensive guide, we’re diving deep into CRLF Injection — what it is, why it’s dangerous, and how to find and exploit it like a pro. Whether you’re a bug bounty hunter, a penetration tester, or a developer, this is a must-read! Let’s get started!

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🎯 What is CRLF Injection?

CRLF (Carriage Return Line Feed) Injection is a web security vulnerability that allows attackers to inject Carriage Return (CR) and Line Feed (LF) characters into web application inputs. These characters are used to signify the end of a line in text-based protocols such as HTTP.

🔍 Why is it Dangerous?

CRLF injection can be used for:

• HTTP Response Splitting: Split a single HTTP response into two, allowing attackers to control the second response (e.g., malicious redirects or XSS).
• Log Poisoning: Inject fake entries into server logs to cover tracks or trigger false alerts.
• XSS Escalation: Bypass sanitization by injecting HTML/JavaScript via headers.
• Email Header Injection: Manipulate email headers (e.g., BCC attackers in password reset emails).

🔑 CRLF Breakdown: What are CR and LF?

• CR (Carriage Return): ASCII code 13 or \r
• LF (Line Feed): ASCII code 10 or \n

Together, they form a new line (\r\n) in many operating systems and protocols. In the context of HTTP, they’re used to separate headers from the body.

📚 CRLF 101: Breaking Down the Basics

🔍 How CRLF Works in HTTP Headers

A normal HTTP response looks like this:

HTTP/1.1 200 OK  
Content-Type: text/html  
Set-Cookie: session=abc123