If traffic gets fragmented, only the first fragment is parsed for headers. If the Host header is not in the first fragment, the request is not handled. Example:
(echo -n $'GET / HTTP/1.1\r\n'; sleep 2; echo -n $'Host: test\r\n\r\n') | nc -q 1 vost 80
If traffic gets fragmented, only the first fragment is parsed for headers. If the Host header is not in the first fragment, the request is not handled. Example: