pinoc has posted instructions that I believe are very straightforward.
Quoting here for your convenience:
b) if you have done a logout or reboot after the upgrade
trying to login will return you immediately to the login window
-reboot and at the grub boot menu press the F3 key which will open a little window with the value Default preselected, press the Enter key and you will see a command line at the bottom of the screen.
- scroll to the end of that line and enter a space and the number 3, so the end of that line reads:
splash=silent vga=788 3
then press the Enter key.
- when the boot process has finished login as user root and enter your root-password
- then enter these 4 commands:
rpm -e --nodeps libopenssl1.0.0 libopenssl-devel libopenssl-engines1.0.0 openssl
apt-get install --fix-broken -y
Try that solution and come back if this doesn't work.
After each command in terminal, you have to press enter.
I'm currently not affected by this issue because I didn't update yesterday so I can't provide a more detailed guide.