If the computer exists it can theoretically be compromised, it just depends on the resources of the individual or group attempting to compromise it. For example, the US Government created Stuxnet targetting the completely airgapped computers which operated centrifuges in Iran. They created brand new malware, loaded it onto flashdrive and sprinkled said flashdrives near the target, then sat and waited then observed their nuclear refinement centrifuges fail way more rapidly than they should effectively killing their nuclear program