While changing the password of internal oracle users in oracle 12c , after it got expired, you may get error as below.


ORA-600:[kpdbModAdminPasswdInRoot: Not CDB]

SQL> connect system/oracle
ORA-28001: the password has expired

Changing password for system
New password:
Retype new password:
ORA-00600: internal error code, arguments: [kpdbModAdminPasswdInRoot: not CDB],
[], [], [], [], [], [], [], [], [], [], []

Password unchanged
Warning: You are no longer connected to ORACLE.


Apply the patch 16901482 on the respective ORACLE_HOME.

Reference ( Doc ID 1583225.1 )