On your CentOS machine, assuming that you didn't install OpenSCAP during operating system installation, follow this:
sudo yum install openscap-scanner scap-security-guide
On the Ubuntu machine, do this:
sudo apt install python-openscap
On your CentOS machine, assuming that you didn't install OpenSCAP during operating system installation, follow this:
sudo yum install openscap-scanner scap-security-guide
On the Ubuntu machine, do this:
sudo apt install python-openscap