It depenends a bit on what you want to do.
If you just want to block /CFIDE you can just use a PredicateHandler, with a PathPrefixPredicate, and if it matches use ResponseCodeHandler to return the desired response code. You could combine it with io.undertow.server.handlers.AccessControlListHandler or io.undertow.server.handlers.IPAddressAccessControlHandler if you want to limit the IP range.
Basically you just use a predicate to decide what you want to restrict, and then map it to a handler that either rejects the request outright or performs an access control check.
Stuart