Iñaki Baz Castillo writes:
How to handle it? is it not a real security hole?
1) buy pstn gws that accept no hostnames (just its own ip address) in
the hostpart of r-uri. example, cisco ios with later software
releases.
2) forget the hostpart check all together and instead check the
userpart, where you have put something special that the gw then
removes.
-- juha