ORA-28002

ORA-28002: the password will expire within 5 days.

Cause: The user's account is about to about to expire and the password needs 
to be changed.

Action: Change the password or contact the database administrator.

Solutions:

1) Simply change the password to avoid it temporary.
 [oracle@sujeet ~]$ sqlplus / as sysdba


SQL> conn system/password

ERROR:
ORA-28002: the password will expire within 5 days

Connected.

 [oracle@sujeet ~]$ sqlplus / as sysdba

SQL> alter user system identified by password;

User altered.

SQL> conn system/password

Connected.

2) Set PASSWORD_LIFE_TIME of the profile assigned user to UNLIMITED then 
change the password to avoid it permanently.

SQL> SELECT PROFILE FROM dba_users WHERE username = 'system';

PROFILE
--------------------------------------------------------------------------------
DEFAULT

SQL> SELECT  LIMIT FROM DBA_PROFILES WHERE PROFILE='DEFAULT' AND RESOURCE_NAME='PASSWORD_LIFE_TIME';

LIMIT
--------------------------------------------------------------------------------
180

 [oracle@sujeet ~]$ sqlplus / as sysdba

SQL> ALTER PROFILE DEFAULT LIMIT PASSWORD_LIFE_TIME UNLIMITED;

Profile altered.

SQL> SELECT ACCOUNT_STATUS FROM DBA_USERS WHERE USERNAME='system';

ACCOUNT_STATUS
--------------------------------
OPEN

SQL> conn system/password

Connected.

Issue Resolved.