Yes, just because universe is not supported by Canonical, it doesn't mean it can't get security updates. In this case, the source for krb5 is in main, while some binaries (krb5-user) are in universe.
** Changed in: krb5 (Ubuntu) Status: Unconfirmed => Rejected -- broken dependencies with krb5 packages https://launchpad.net/bugs/88720 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs