Oracle password has expired, however I have no way of changing it
If the account is locked, as far as I know, the user can't change it. The Oracle output in your question shows the account is not locked, but expired.

Log in to your database as a user who has privilege to alter other users (for example, SYS) and issue the following command:

ALTER USER tmpdbo IDENTIFIED BY new_password;


You can change the expiration behaviour. There already was a question about that on Stack Overflow:

Make Oracle Password Never Expire