very good tuturial
https://utopianknight.com/malware/cuckoo-installation-on-ubuntu-20/
*pay attention on step 85:
replace eth0 to your primary adaptor name (you can get it by Ifconfig)
sudo iptables -A FORWARD -o eth0 -i vboxnet0 -s 192.168.56.0/24 -m conntrack --ctstate NEW -j ACCEPT 
then 
sudo iptables -A FORWARD -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT 
then 
sudo iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE