SFTP connection through Java asking for weird authentication

While the solution in the self-accepted answer is correct, it lacks any explanation.

The problem is that the OP have a Kerberos/GSSAPI authentication set as the preferred (the JSch default). Yet OP does not seem to actually use/want it, as OP claims not to specify any username or password for the Kerberos prompts.

This problem can appear spontaneously, when either Kerberos gets installed on the the client PC or the server starts to support Kerberos.

The solution is to remove the Kerberos/GSSAPI (gssapi-with-mic) from the list of preferred authentication methods in JSch:

session.setConfig(
    "PreferredAuthentications", "publickey,keyboard-interactive,password");

Thought I'd post an answer here since in case anyone else ends up running into a similar issue. Turns out I am missing a piece of code that makes all the difference. I just needed to add

session.setConfig("PreferredAuthentications", 
                  "publickey,keyboard-interactive,password");

before

session.connect();

and everything works perfectly now.