CVSROOT

:ssh;username=benutzer;password=P@SSW0RD;hostname=cvsserver:/path/to/repository

Das wird im Hintergrund ausgeführt

cvs -d :ssh;username=benutzer;password=P@SSW0RD;hostname=cvsserver:/path/to/repository login 
Logging in to :ssh:benutzer@cvsserver:22:/path/to/repository
Question: Security Alert
The server's host key is not cached in the registry. You
have no guarantee that the server is the computer you
think it is.
The server's key fingerprint is:
ssh-rsa 1024 02:61:0a:3b:6e:39:db:12:a4:aa:19:dd:1a:68:40:0f
If you trust this host, hit Yes to add the key to
PuTTY's cache and carry on connecting.
If you want to carry on connecting just once, without
adding the key to the cache, hit No.
If you do not trust this host, hit Cancel to abandon the
connection.
Enter: Yes/No/Cancel

***** CVS exited normally with code 0 *****