irule to block a non valid url

Hello cg1603​ 
From your example seems that host header is malformed also

So my first approach would be to accept only valid host header as a starting point with an irule like this

when HTTP_REQUEST 
{
    switch -- [string tolower [HTTP::host]] 
	{
        "www.example.com"
		{
            # Valid Host — allow request
            return
        }
        default 
		{
            log local0. "Blocked invalid Host: $host from [IP::client_addr]"
            HTTP::respond 403 content "Forbidden - Invalid Host"
        }
    }
}