My comment was a little long so I'm putting it in an answer; although I have NOT had to do this myself, it's where I would start.
1) Check if there is a previous kernel listed on the grub boot menu. If so, try that one. If that works, all you have to do is edit
The 0 is relative to the first entry, so if you want to use the next one down instead, change it to "1".
2) If that does not work, there is the possibility of rolling back an update using yum. It looks to me like the basic idea is you use
yum history list to view a table of recent activities (works for me), then you can use
yum undo [N] where
N is an ID index from the table.
Of course for that, you at least need to be able to boot in to a terminal. If you can ssh, you could try that. If there is a "rescue mode" option in your grub menu, try that. Otherwise, boot a live CD and mount your partition so you can change from a graphical boot to a console boot (might help...).
That means changing the
/etc/systemd/system/default.target symlink, which right now is to
/usr/lib/systemd/system/graphical.target. As root:
ln -s /usr/lib/systemd/system/multi-user.target /etc/systemd/system/default.target