On systems where screen is version 4.5.0 (Screen version 4.05.00 (GNU) 10-Dec-16), and setuid root, you can use it to create arbritary files with root permissions containing arbritary content.
This PoC creates an /etc/ld.so.preload file pointing to a library that creates a setuid root shell and then calls screen again to trigger it.
TL;DR you get root.
Original bug report is here
Install this version of screen.
wget https://ftp.gnu.org/gnu/screen/screen-4.5.0.tar.gz tar -xf screen-4.5.0.tar.gz cd screen-4.5.0 ./configure make sudo make install
Now you have an exploitable version.