This question already has an answer here:
Let's assume that I'm on someone others network where DNS etc is configured through DHCP.
So when I want to connect to the VPN service the DNS servers on the network that I am connected to return a local IP instead of the real one for my VPN service.
The MItM VPN service just happily accepts all credentials and forwards them to the real service.
I think that my connection is safe, but the MItM service have all traffic without encryption.
Is the above possible or does the authentication mechanism in VPN make sure that both parties are who they say that they are?