> 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/host-header/bypassing-validation-by-connection-state.md).
# Bypassing Validation by Connection State
Bypassing Validation by Connection State notes for PortSwigger Web Security Academy labs, including exploitation workflow, payload testing, Burp Suite validation, and remediation context.
### Host Validation Bypass via Connection State Attack
**Description of vulnerability**
This lab has a **SSRF-type vulnerability based on routing via Host** header, linked to poor status management of the server-side connection.
Although the front server seems to properly validate the `Host` header, it makes a dangerous \*\* hypothesis\*\*:
> All requests sent on the same TCP connection are considered reliable if the **first request** is valid.
This allows to inject a later malicious request on the same connection, bypassing the initial validation.
**Lab objective**
* Access the internal administration panel:/ `HTTP://192.168.0.1/admin`
* Delete user **carlos**
**Observation initiale**
A direct request to internal IP is blocked:
```http
GET / HTTP/1.1
Host: 192.168.0.1
```
The server rejects this request, which confirms that a `Host` validation is in place **at the first request**.
**Operation: connection state attack**
The idea is to send \*\* several requests on the same TCP connection\*\*:
1. A legitimate first request to the public host (accepted).
2. A second malicious request to internal IP, sent **on the same connection**.
In Burp Suite, this is done by:
* Grouping requests
* Using **Send group in single connection**
**Access to the administration panel**
Once the connection is established with a valid query, the following request to the internal admin is accepted:
```http
GET /admin HTTP/1.1
Host: 192.168.0.1
```
The internal administration panel then becomes accessible.
**Deletion of the user**
Removing the user requires a POST query:
```http
POST /admin/delete HTTP/1.1
Host: 192.168.0.1
csrf=ppBVKn8wVrgZifEETHsn48Hykwiq8yFO&username=carlos
```
Server response:
---
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