Possibly related to the recent change in: MDEV-22313

The default role is set to 0 (which is incorrect).

# mysql mysql -se "show grants for 'user1'@'localhost';"

Grants for user1@localhost

GRANT USAGE ON *.* TO `user1`@`localhost` IDENTIFIED BY PASSWORD '*REDACTED'

SET DEFAULT ROLE 0 FOR 'user1'@'localhost'

This causes database users to have invalid grants.

Reading access rights for the cPanel user “user1” from live data:

 MariaDB/MySQL …Invalid grant string: SET DEFAULT ROLE 0 FOR 'user1'@'localhost'

This breaks the cPanel "Databases" interface. (Screenshot attached) This does not occur for all servers that update to these versions and the cause of some of them breaking has yet to be determined.

Downgrading solves the issue. Additionally, another workaround that we have used is to set the default role to NONE.

MariaDB [(none)]> SET DEFAULT ROLE none FOR 'user1'@'localhost';

 Query OK, 0 rows affected (0.000 sec)