Uncover the Shocking Truth Behind HTTP Header Injection Attacks: Protect Yourself Now!

Discover the Techniques and Defenses Against Devastating HTTP Header Injection Attacks

HTTP Header Injection is a web security vulnerability that allows an attacker to manipulate HTTP headers by injecting arbitrary data into a web application’s response headers. This can lead to various malicious activities, including cross-site scripting (XSS), cross-user defacement, web cache poisoning, etc. This article dives deep into HTTP Header Injection, and its types, and provides practical examples and cheat sheets for better understanding.

HTTP Header Injection occurs when user input is insecurely included in the headers of an HTTP response. This can happen due to improper validation or escaping of input data. When exploited, it allows attackers to inject malicious payloads into the headers, affecting how the server or client interprets the HTTP response.

Response SplittingHTTP Response SmugglingXSS via HTTP HeadersCross-User DefacementWeb Cache Poisoning

1. Response Splitting

Response splitting occurs when an attacker injects newline characters (\r\n) into an HTTP header, allowing them to craft multiple HTTP responses from a single request. This can lead to cache poisoning, XSS, and other attacks.

Example:

GET /example HTTP/1.1
Host: vulnerable.com
User-Agent: evil-ua\r\nHTTP/1.1 200 OK\r\nContent-Type: text/html\r\nContent-Length: 0\r\n\r\n<script>alert('Injected!');</script>

2. HTTP Response Smuggling

HTTP Response Smuggling happens when inconsistencies in how different systems interpret HTTP headers allow an attacker to hide malicious requests, bypassing security controls or causing unexpected behaviors.

Example:

POST /vulnerable HTTP/1.1
Host: vulnerable.com
Content-Length: 13
Transfer-Encoding: chunked

HTTP/1.1 200 OK
Content-Type: text/html

<script>alert('Injected!');</script>

3. XSS via HTTP Headers

Attackers can inject JavaScript payloads into HTTP headers like Location, Referer, or Set-Cookie, which are then executed in the context of the user's browser.

Example:

HTTP/1.1 200 OK
Content-Type: text/html
Location: javascript:alert('XSS')

4. Cross-User Defacement

This type of attack occurs when an attacker injects content that gets reflected to other users, often through HTTP headers like Content-Disposition or Content-Type.

Example:

HTTP/1.1 200 OK
Content-Type: text/html
Content-Disposition: attachment; filename="evil.html"

5. Web Cache Poisoning

In web cache poisoning, an attacker manipulates HTTP headers to store malicious content in a shared cache, affecting all users who subsequently access the poisoned cache.

Example:

HTTP/1.1 200 OK
Content-Type: text/html
Cache-Control: max-age=3600

References:

Input Validation: Ensure that all user inputs are properly validated and sanitized.Output Encoding: Encode data before including it in HTTP headers.Use of Security Libraries: Implement security libraries and frameworks that automatically handle input validation and output encoding.Content Security Policy (CSP): Implement CSP to restrict the types of content that can be loaded on your web pages.Web Application Firewalls (WAF): Deploy WAFs to detect and block malicious traffic.