17 Jan, 2023

HTTP request smuggling

Vulnerability Assessment as a Service (VAaaS)

Tests systems and applications for vulnerabilities to address weaknesses.

The Abbreviation for HTTP request smuggling is “HTTP Smuggling” or “HTTPRS”.

HTTP Request Smuggling is a technique used to exploit a vulnerability in web servers or proxy servers that results from the way they parse and process HTTP requests. The vulnerability can be exploited to cause the server to misinterpret the request and perform unintended actions, such as bypassing security controls or access restricted resources. This technique can also be used to launch a variety of attacks, such as cross-site scripting (XSS) and denial of service (DoS). This can allow attackers to send a second, illegitimate request that is not detected or blocked by the server, allowing them to bypass security controls or conduct malicious actions such as injecting malware or stealing sensitive data. It is important to keep software up to date and to properly configure web servers to prevent HTTP request smuggling attacks.

HTTP smuggling is a vulnerability that occurs when multiple HTTP requests with the same destination host and port are sent to a server and processed differently, leading to unintended behavior.

Generally to identify HTTP Request Smuggling vulnerabilities using Burp Suite, you can use the following steps:

1. Send a normal request to the target server using the Burp Suite proxy.

2. Modify the request to include multiple requests with the same host and port, using either the Content-Length or Transfer-Encoding header to smuggle the extra request.

3. Observe the server’s response and look for any unexpected behavior, such as additional requests being processed or incorrect responses being returned.

4. Confirm the vulnerability by repeating the process with different variations of the request.

Here’s an example of how you can use Burp Suite to identify a Content-Length Smuggling vulnerability:

1. First, send a request to the target application using Burp Suite’s Proxy tool.

2. After capturing the request, you can use the Repeater tool to modify the request and try different payloads.

3. To test for Content-Length Smuggling, you can modify the Content-Length header in the request to be larger or smaller than the actual size of the request body.

4. If the target application is vulnerable to Content-Length Smuggling, you may observe different behavior in the response, such as unexpected error messages, incomplete responses, or slow response times.

5. If the target application is not vulnerable, you may observe that the response is unchanged.

Here’s an example of how you can use Burp Suite to identify a Transfer-Encoding Smuggling vulnerability:

1. First, send a request to the target application using Burp Suite’s Proxy tool.

2. After capturing the request, you can use the Repeater tool to modify the request and try different payloads.

3. To test for Transfer-Encoding Smuggling, you can add the following header to the request:

				
					Transfer-Encoding: chunked
				
			

4. If the target application is vulnerable to Transfer-Encoding Smuggling, you may observe different behavior in the response, such as unexpected error messages, incomplete responses, or slow response times.

5. If the target application is not vulnerable, you may observe that the response is unchanged.

Those steps are just one way to identify HTTP Request Smuggling vulnerabilities using Burp Suite, and that the exact method used may vary depending on the specific implementation and configuration of the server.

Common exploitation examples of HTTP Request Smuggling vulnerabilities

1. Content-Length Smuggling: This type of smuggling occurs when the server relies on the Content-Length header to determine the length of the request body, but the header value is manipulated to smuggle an additional request. For example, a malicious attacker could send a request with a Content-Length header value that is larger than the actual request body, and the server may process an additional request that was appended to the original request.

				
					GET /example HTTP/1.1
Host: www.example.com
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:122.0) Gecko/20100101 Firefox/122.0
Accept: text/html,application/xhtml+xml,appliGET /example HTTP/1.1
Host: www.example.com
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:122.0) Gecko/20100101 Firefox/122.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Connection: close
Content-Length: 20

GET /another-example HTTP/1.1
Host: www.example.com
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:122.0) Gecko/20100101 Firefox/122.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Connection: close
Upgrade-Insecure-Requests: 1
cation/xml;q=0.9,image/webp,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Connection: close
Upgrade-Insecure-Requests: 1
				
			

In this example, the first request includes the Content-Length header with a value of 20. The second request has been added after the first request, separated by a blank line. This request is to the URL http://www.example.com/another-example. The two requests have different headers and values.

This is an example of a Smuggled Request using Content-Length smuggling, as the server may misinterpret the length of the first request and process the second request as part of the first, leading to unexpected behavior and potentially exploitable vulnerabilities, including HTTP Request Smuggling.

2. Transfer-Encoding Smuggling: This type of smuggling occurs when the server relies on the Transfer-Encoding header to determine the encoding of the request body, but the header value is manipulated to smuggle an additional request. For example, a malicious attacker could send a request with a Transfer-Encoding: chunked header and a Content-Length header, and the server may process an additional request that was appended to the original request.

				
					GET /example HTTP/1.1
Host: www.example.com
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:122.0) Gecko/20100101 Firefox/122.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Connection: close
Transfer-Encoding: chunked

GET /another-example HTTP/1.1
Host: www.example.com
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:122.0) Gecko/20100101 Firefox/122.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Connection: close
Upgrade-Insecure-Requests: 1

				
			

In this example, the first request includes the Transfer-Encoding header with a value of chunked. The second request has been added after the first request, separated by a blank line. This request is to the URL http://www.example.com/another-example. The two requests have different headers and values.

This is an example of a Smuggled Request using Transfer-Encoding smuggling, as the server may misinterpret the encoding of the first request and process the second request as part of the first, leading to unexpected behavior and potentially exploitable vulnerabilities, including HTTP Request Smuggling.

In Burp Suite, you can modify this request and add, remove, or modify headers, or change the request method to see how the server responds to different requests. This can be useful for testing and identifying vulnerabilities, including HTTP Smuggling.

These two examples are common because many web servers rely on the Content-Length and Transfer-Encoding headers to determine the structure of HTTP requests, and these headers are frequently manipulated in HTTP Request Smuggling attacks. It’s important to always validate inputs and follow security best practices to prevent vulnerabilities in your applications.

Privilege escalation techniques related to HTTP Request Smuggling vulnerabilities

List of privilege escalation techniques that can be used with HTTP Request Smuggling vulnerability:

1. Impersonation: Modifying the request headers to impersonate a higher-privileged user.

2. Resource Smuggling: Smuggling a request to a different, higher-privileged resource.

3. Access Bypass: Bypassing access controls to access sensitive information or perform privileged actions.

4. Unauthorized Actions: Injecting additional requests to perform unauthorized actions.

5. Parameter Tampering: Tampering with the parameters of the request to alter the processing by the back-end server.

6. Sensitive Resource Access: Smuggling requests to sensitive resources that would normally be protected by access controls.

7. Logic Bug Exploitation: Exploiting logic bugs in the application to gain higher privileges.

8. Code Injection: Injecting malicious code into the request to execute arbitrary code on the back-end server.

9. Security Measure Bypass: Bypassing rate-limiting or other security measures.

10. Sensitive Data Access: Smuggling requests to bypass security measures and gain access to sensitive data.

General methodology and checklist for HTTP Request Smuggling vulnerabilities

The general methodology for testing HTTP Request Smuggling vulnerabilities can be summarized in the following steps:

1. Research and Discovery: Research on the technology stack and architecture of the target system, and identify potential areas for request smuggling.

2. Configuration Analysis: Analyze the configuration of the target system, including the HTTP and Web server settings, to identify potential weaknesses.

3. Request Analysis: Analyze the requests being sent to the target system, looking for potential vectors for request smuggling.

4. Vulnerability Verification: Verify the presence of request smuggling by injecting malicious payloads into the requests and observing the response from the target system.

5. Exploitation: Attempt to exploit the request smuggling vulnerability to escalate privileges, bypass security measures, or access sensitive data.

6. Reporting: Document the findings and provide a comprehensive report to the stakeholders, including recommendations for remediation.

A checklist for testing HTTP Request Smuggling vulnerabilities would include the following items:

  • Verify if the target system supports HTTP pipelining.

  • Check for presence of reverse proxies and load balancers.

  • Check for processing of multiple requests in a single connection.

  • Check for processing of multiple Content-Length headers.

  • Check for processing of multiple Transfer-Encoding headers.

  • Check for processing of invalid requests.

  • Check for processing of overlapping requests.

  • Check for processing of malicious payloads in the requests.

  • Verify if the target system is vulnerable to HTTP Request Smuggling attacks.

  • Attempt to exploit the vulnerability to escalate privileges or access sensitive data.

Tools set for exploiting HTTP Request Smuggling vulnerabilities

Manual Tools:

1. Burp Suite: а popular web application security testing tool that can be used for manual testing and exploitation of HTTP Request Smuggling vulnerabilities.

2. OWASP ZAP: аn open-source web application security scanner that can be used to identify and exploit HTTP Request Smuggling vulnerabilities.

3. Fiddler: а free, multi-platform web debugging proxy that can be used to intercept and modify HTTP requests for manual testing of HTTP Request Smuggling vulnerabilities.

4. Telerik Fiddler: а web debugging proxy that can be used to test and debug HTTP traffic.

5. Wireshark: а free, open-source network protocol analyzer that can be used to analyze and inspect HTTP traffic for manual testing of HTTP Request Smuggling vulnerabilities.

6. Netcat: а simple and versatile network utility that can be used to test HTTP connectivity and exploit HTTP Request Smuggling vulnerabilities.

Automated Tools:

1. Acunetix: а web application security scanner that can be used to automate the discovery and exploitation of HTTP Request Smuggling vulnerabilities.

2. Nessus: a comprehensive vulnerability scanner that can be used to identify and exploit HTTP Request Smuggling vulnerabilities.

3. Nmap: a free, open-source network mapper that can be used to automate the discovery and exploitation of HTTP Request Smuggling vulnerabilities.

4. sqlmap: an open-source tool for automating the discovery and exploitation of SQL injection vulnerabilities.

5. OWASP DirBuster: an open-source directory brute-forcing tool that can be used to automate the discovery and exploitation of HTTP Request Smuggling vulnerabilities.

6. Metasploit Framework: an open-source framework for developing and executing exploits that can be used to automate the exploitation of HTTP Request Smuggling vulnerabilities.

7. Arachni: a web application security scanner that can be used to automate the discovery and exploitation of HTTP Request Smuggling vulnerabilities.

8. Nikto: an open-source web server scanner that can be used to automate the discovery and exploitation of HTTP Request Smuggling vulnerabilities.

9. Skipfish: an open-source web application security scanner that can be used to automate the discovery and exploitation of HTTP Request Smuggling vulnerabilities.

Browser Plugins:

1. TamperData: a browser plugin for Firefox that can be used to modify HTTP requests in real-time for manual testing of HTTP Request Smuggling vulnerabilities.

2. Requestly: a browser plugin for Chrome and Firefox that can be used to modify HTTP requests in real-time for manual testing of HTTP Request Smuggling vulnerabilities.

3. Edit This Cookie: a browser plugin for Chrome and Firefox that can be used to manipulate cookies for manual testing of HTTP Request Smuggling vulnerabilities.

4. ModHeader: a browser plugin for Chrome and Firefox that can be used to modify HTTP headers in real-time for manual testing of HTTP Request Smuggling vulnerabilities.

5. Live HTTP Headers: a browser plugin for Firefox that can be used to inspect HTTP headers in real-time for manual testing of HTTP Request Smuggling vulnerabilities.

Average CVSS score of HTTP Request Smuggling vulnerabilities

CVSS (Common Vulnerability Scoring System) is a widely adopted open industry standard for evaluating the severity of a vulnerability. CVSS assigns a score to a vulnerability based on its potential impact and the ease of exploitation.

The average CVSS score for HTTP Request Smuggling vulnerabilities varies depending on the specific vulnerability and the environment in which it exists. Generally, the CVSS score for HTTP Request Smuggling vulnerabilities is in the range of 6.0 to 8.0, which is considered to be a medium to high severity. The exact score depends on various factors, such as the potential impact of the vulnerability and the ease of exploiting it.

In some cases, HTTP Request Smuggling vulnerabilities can be used to gain unauthorized access to sensitive information, compromise systems, or carry out a Denial of Service (DoS) attack. These types of vulnerabilities often receive a higher CVSS score as they pose a significant risk to the organization and its assets.

Always remember CVSS is just one factor in evaluating the severity of a vulnerability and should be used in conjunction with other risk assessment methods and considerations specific to an organization’s environment.

The Common Weakness Enumeration (CWE) for HTTP Request Smuggling vulnerabilities

HTTP Request Smuggling vulnerabilities can fall under several CWE categories, including:

CWE-113: Improper Neutralization of CRLF Sequences in HTTP Headers: This category refers to improper handling of carriage return/line feed (CRLF) sequences in HTTP headers, which can be used to smuggle malicious requests into a target system.

CWE-287: Improper Authentication: This category refers to weaknesses in the authentication process that can allow attackers to bypass security controls and access sensitive information or systems.

CWE-20: Improper Input Validation: This category refers to weaknesses in the validation of user-supplied input that can allow attackers to inject malicious payloads into the application.

CWE-352: Cross-Site Request Forgery (CSRF): This category refers to weaknesses in the application’s protection against cross-site request forgery attacks, where an attacker tricks a user into making a request to a vulnerable application.

CWE-472: External Control of System or Configuration Setting: This category refers to weaknesses in the application’s control over system settings or configuration, which can be exploited by attackers to modify settings or gain unauthorized access.

CWE-78: Improper Neutralization of Special Elements used in a Command (OS Command Injection): This category refers to weaknesses in the application’s neutralization of special elements used in operating system commands, which can be exploited by attackers to inject malicious commands into the system.

CWE-22: Improper Limitation of a Pathname to a Restricted Directory (‘Path Traversal’): This category refers to weaknesses in the application’s limitation of file paths to restricted directories, which can be exploited by attackers to access files or directories outside the intended scope.

CWE-79: Improper Neutralization of Input During Web Page Generation (‘Cross-site Scripting’): This category refers to weaknesses in the application’s neutralization of user-supplied input during web page generation, which can be exploited by attackers to inject malicious scripts into the page.

Understanding these categories can help organizations prioritize their security efforts and take action to mitigate the risks associated with HTTP Request Smuggling vulnerabilities.

Top 10 latests CVE related to HTTP Request Smuggling vulnerabilities

CVE-2022-42252  – If Apache Tomcat 8.5.0 to 8.5.82, 9.0.0-M1 to 9.0.67, 10.0.0-M1 to 10.0.26 or 10.1.0-M1 to 10.1.0 was configured to ignore invalid HTTP headers via setting rejectIllegalHeader to false (the default for 8.5.x only), Tomcat did not reject a request containing an invalid Content-Length header making a request smuggling attack possible if Tomcat was located behind a reverse proxy that also failed to reject the request with the invalid header.

CVE-2022-41721 – A request smuggling attack is possible when using MaxBytesHandler. When using MaxBytesHandler, the body of an HTTP request is not fully consumed. When the server attempts to read HTTP2 frames from the connection, it will instead be reading the body of the HTTP request, which could be attacker-manipulated to represent arbitrary HTTP2 requests.

CVE-2022-38114 – This vulnerability occurs when a web server fails to correctly process the Content-Length of POST requests. This can lead to HTTP request smuggling or XSS.

CVE-2022-36760 – Inconsistent Interpretation of HTTP Requests (‘HTTP Request Smuggling’) vulnerability in mod_proxy_ajp of Apache HTTP Server allows an attacker to smuggle requests to the AJP server it forwards requests to. This issue affects Apache HTTP Server Apache HTTP Server 2.4 version 2.4.54 and prior versions.

CVE-2022-35256 – The llhttp parser in the http module in Node v18.7.0 does not correctly handle header fields that are not terminated with CLRF. This may result in HTTP Request Smuggling.

CVE-2022-32215 – The llhttp parser <v14.20.1, <v16.17.1 and <v18.9.1 in the http module in Node.js does not correctly handle multi-line Transfer-Encoding headers. This can lead to HTTP Request Smuggling (HRS).

CVE-2022-32214 – The llhttp parser <v14.20.1, <v16.17.1 and <v18.9.1 in the http module in Node.js does not strictly use the CRLF sequence to delimit HTTP requests. This can lead to HTTP Request Smuggling (HRS).

CVE-2022-32213 – The llhttp parser <v14.20.1, <v16.17.1 and <v18.9.1 in the http module in Node.js does not correctly parse and validate Transfer-Encoding headers and can lead to HTTP Request Smuggling (HRS).

CVE-2022-26377 – Inconsistent Interpretation of HTTP Requests (‘HTTP Request Smuggling’) vulnerability in mod_proxy_ajp of Apache HTTP Server allows an attacker to smuggle requests to the AJP server it forwards requests to. This issue affects Apache HTTP Server Apache HTTP Server 2.4 version 2.4.53 and prior versions.

CVE-2022-2880 – Requests forwarded by ReverseProxy include the raw query parameters from the inbound request, including unparseable parameters rejected by net/http. This could permit query parameter smuggling when a Go proxy forwards a parameter with an unparseable value. After fix, ReverseProxy sanitizes the query parameters in the forwarded query when the outbound request’s Form field is set after the ReverseProxy. Director function returns, indicating that the proxy has parsed the query parameters. Proxies which do not parse query parameters continue to forward the original query parameters unchanged.

The list of CVEs is constantly being updated and full an up-to-date list of all existed Common Vulnerabilities and Exposures (CVEs) for HTTP Request Smuggling vulnerabilities can be found at official CVE website https://cve.mitre.org/

List of popular exploits related to HTTP Request Smuggling vulnerabilities

The most common exploits for HTTP Request Smuggling vulnerabilities:

1. Transfer-Encoding smuggling: A malicious request can be sent to the target system with a Transfer-Encoding header that is not properly handled by the server. This can result in the target system treating the request body as a separate request, leading to request smuggling.

2. Content-Length smuggling: A malicious request can be sent to the target system with a Content-Length header that is not properly handled by the server. This can result in the target system treating the request body as a separate request, leading to request smuggling.

3. Request splitting: A malicious request can be split into two separate requests, with the first request carrying the header information and the second request carrying the payload. This can result in the target system processing the two separate requests as a single request, leading to request smuggling.

4. Header injection: A malicious request can be sent to the target system with a header that is not properly handled by the server. This can result in the target system treating the request body as a separate request, leading to request smuggling.

5. URL encoding: A malicious request can be sent to the target system with a URL that is not properly encoded. This can result in the target system treating the request body as a separate request, leading to request smuggling.

Practice identifying and exploiting HTTP Request Smuggling vulnerabilities

To practice HTTP Request Smuggling vulnerabilities, I would recommend the following steps:

1. Read and understand the concepts of HTTP Request Smuggling, including the different types of Smuggling attacks and their impact.

2. Set up a lab environment with virtual machines to test and practice exploitation techniques.

3. Familiarize yourself with various tools used for exploiting HTTP Request Smuggling, such as Burp Suite, ZAP, and OWASP ZSC.

4. Use online resources such as blogs, articles, and video tutorials to gain a deeper understanding of HTTP Request Smuggling and its exploitation techniques.

5. Practice exploiting HTTP Request Smuggling vulnerabilities on vulnerable web applications or services. You can use vulnerable applications or services that have been specifically designed for testing purposes, or you can use real-world examples if you have permission to do so.

6. Review the results of your tests and analyze the impact of your exploitation techniques. Try to identify any weaknesses in your approach and find ways to improve your skills.

7. Repeat the above steps to build your knowledge and experience.

Some resources where you can practice HTTP Request Smuggling vulnerabilities:

1. OWASP WebGoat Project – a free, open-source, deliberately insecure web application provided as a safe environment for security testing and education.

2. Hack The Box – a platform that offers a variety of challenges and vulnerable systems for testing and improving your skills.

3. Bug Bounty Platforms – websites such as HackerOne and Bugcrowd offer programs where you can test for vulnerabilities and earn rewards for responsibly reporting them.

4. Metasploitable – a vulnerable virtual machine that can be used for testing and developing exploits.

5. PortSwigger’s Web Security Academy – a free learning platform that offers challenges and tutorials on various web security topics, including HTTP Request Smuggling.

These resources are for educational and testing purposes only and should not be used to attack real websites or systems.

Books with review of HTTP Request Smuggling vulnerabilities

List of books that you may find helpful in learning about HTTP request smuggling vulnerabilities:

1. “Web Application Hacker’s Handbook: Discovering and Exploiting Security Flaws” by Dafydd Stuttard and Marcus Pinto is a comprehensive guide to finding and exploiting security vulnerabilities in web applications. The book covers a wide range of topics, from basic attacks such as SQL injection and XSS, to more advanced attacks such as HTTP request smuggling. This book is well-regarded in the security community for its technical depth and practical approach.

2. “The Browser Hacker’s Handbook” by Wade Alcorn, Christian Frichot, Michele Orru, and Ferruh Mavituna is a comprehensive guide to the inner workings of web browsers and how to exploit vulnerabilities in them. The book covers a wide range of topics, including HTTP request smuggling, and provides a deep understanding of the underlying technologies that enable these attacks.

3. “Gray Hat Hacking: The Ethical Hacker’s Handbook” by Allen Harper, Shon Harris, Jonathan Ness, Chris Eagle, Gideon Lenkey, and Terron Williams is a comprehensive guide to the art of ethical hacking. The book covers a wide range of topics, including HTTP request smuggling, and provides practical advice and guidance on how to test and exploit security vulnerabilities in a responsible manner.

4. “The Basics of Hacks and Hacking: A Guide for Beginners to Ethical Hacking” by Mr. Iddris Sandu is a beginner-friendly guide to the world of hacking and ethical hacking. The book covers a range of topics, including HTTP request smuggling, and provides a foundational understanding of the underlying technologies and methods used by hackers.

5. “Hacking: The Art of Exploitation” by Jon Erickson is a classic text on the art of hacking. The book provides a comprehensive overview of the underlying technologies and methods used by hackers to exploit security vulnerabilities, including HTTP request smuggling. The book is widely regarded as a must-read for anyone interested in the field of computer security and hacking.

List of payloads for HTTP Request Smuggling vulnerabilities

HTTP request smuggling payloads can take various forms and techniques, such as:

1. Transfer-Encoding: chunked – This payload involves manipulation of the Transfer-Encoding header, which is used to indicate the encoding of the HTTP body. By specifying chunked encoding, the attacker can send multiple requests in a single HTTP connection, which can allow them to bypass firewalls and other security controls.

2. Content-Length manipulation – This involves manipulating the Content-Length header to manipulate the amount of data being sent in an HTTP request. This can be used to hide payloads or otherwise alter the behavior of an application.

3. Request pipelining – This is the process of sending multiple HTTP requests without waiting for the responses. This can allow an attacker to send requests that are interpreted differently by the server, potentially leading to vulnerabilities.

4. Connection header manipulation – The Connection header is used to control persistent connections in HTTP. By manipulating this header, an attacker can control the behavior of the server, potentially leading to vulnerabilities.

5. HTTP header injection – This is the process of injecting additional headers into an HTTP request, which can be used to modify the behavior of the server.

6. HTTP trailer injection – This is similar to HTTP header injection, but the payload is sent in the trailer of an HTTP message, which can be used to bypass security controls.

7. HTTP parameter pollution – This is the process of injecting additional parameters into an HTTP request, which can be used to modify the behavior of the server.

8. HTTP request splitting – This is the process of splitting an HTTP request into multiple parts, which can be used to bypass security controls.

9. Web cache poisoning – This is the process of injecting malicious content into a web cache, which can be used to serve malicious content to users.

10. Double request smuggling – This is a technique that involves sending two HTTP requests in such a way that one of them is interpreted differently by the server.

11. Slowloris attacks – This is a type of Denial of Service (DoS) attack that works by keeping HTTP connections open for long periods of time.

12. HTTP request header field manipulation – This is the process of manipulating HTTP request headers to modify the behavior of the server.

13. Non-ASCII characters in HTTP requests – This is the use of non-ASCII characters in HTTP requests, which can be used to bypass security controls.

14. HTTP request smuggling via out-of-band channels – This is the process of sending HTTP requests over channels that are not part of the standard HTTP communication, which can be used to bypass security controls.

15. Malicious HTTP redirects – This is the process of redirecting users to malicious sites, which can be used to steal sensitive information or install malware.

16. Multiple HTTP requests within a single packet – This is the process of sending multiple HTTP requests within a single network packet, which can be used to bypass security controls.

17. HTTP request smuggling via multiple domains – This is the process of sending HTTP requests over multiple domains, which can be used to bypass security controls.

18. HTTP request smuggling via misconfigured proxy servers – This is the process of exploiting misconfigured proxy servers to bypass security controls.

19. HTTP request smuggling via misconfigured load balancers – This is the process of exploiting misconfigured load balancers to bypass security controls.

Payloads and techniques used for HTTP request smuggling can change quickly, so it’s important to stay up to date on the latest information and best practices.

Mitigations and how to be protected from HTTP Request Smuggling vulnerabilities

There are several steps that can be taken to protect against HTTP Request Smuggling attacks:

1. Validate user inputs: All inputs should be validated for content and length, to ensure that malicious requests cannot be smuggled into the system.

2. Use a web application firewall (WAF): A WAF is an essential security layer that can detect and block malicious HTTP requests. Some WAFs have specific rules to prevent HTTP request smuggling attacks.

3. Implement proper error handling: Ensure that your web application can handle errors properly, so that it can respond to any malicious requests in a controlled manner.

4. Regularly update software: Keep your software and libraries up-to-date to ensure that any vulnerabilities are patched.

5. Monitor network traffic: Regularly monitor network traffic to identify any suspicious requests that might indicate an HTTP request smuggling attack.

6. Use intrusion detection systems (IDS): IDS systems can detect and alert on any malicious network activity, which can help in identifying and responding to HTTP request smuggling attacks.

7. Educate employees: Ensure that your employees are aware of the dangers of HTTP request smuggling attacks and how to identify them. Regular security training can help to minimize the risk of these attacks.

8. Regularly perform security audits: Regular security audits can identify any vulnerabilities in your systems, which can help in proactively addressing them before they can be exploited by attackers.

By implementing these steps, organizations can significantly reduce the risk of an HTTP request smuggling attack, and improve the overall security of their systems.

Conclusion

HTTP request smuggling is a type of web application vulnerability that exploits the way HTTP requests are processed by servers and intermediate devices such as reverse proxies, load balancers, and caching servers. Attackers can manipulate the content and format of HTTP requests to evade security filters, manipulate the intended target, or interfere with the expected response from the server.

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