I upgraded to Debian 12.15 today, rebooted and checked open ports just to see if all services are running.

To my surprise, MariaDB is no longer listening on 127.0.0.1:3306, but we have "init" listening on :::3306.

It looks like default config has changed to use Systemd sockets. Which I guess is fine, but silently making your database server accessible to the whole Internet doesn't sound like a good idea.

So, just PSA, if you rely on bind-address only, make sure you reconfigure the mariadb.socket settings.