Common UNIX Printing System has become the standard for sharing printers on a linux-network. You will often see port 631 open in your priv-esc enumeration when you run netstat. You can log in to it here: http://localhost:631/admin

You authenticate with the OS-users.

Find a version.

Test cups-config --version.

If this does not work surf to http://localhost:631/printers and see the CUPS version in the title bar of your browser.

There are vulnerabilities for it so check your searchsploit.