How can I replicate this attack?
There are many ways to do this.
The simplest thing to try first might be to just replicate it using "netcat." Netcat is invoked using the "nc" command on Linux (or the "ncat" command on Windows, if you have nmap for Windows installed).
For example, assuming the attacked host was [host] and attacked port was [port], at a Linux command prompt type:
nc [host] [port]
This should open up a connection to [host] on port [port]. Assuming that you connect, you can now type:
GET /current_config/passwd HTTP/1.1
And then hit Enter once.
And then type:
And then hit enter a few times to send the http request (with the Host header). The HTTP response will appear in the terminal if there is one. Hopefully you see a 404 error and not your passwd file.