If you use VMware Fusion, upgrading to macOS 10.15.6 is not the best idea at the moment as this combination inevitably crashes your system.
Recently the news on problems with VMware Fusion and latest macOS 10.15.6, released on July 15th, occurred. These problems often result in a quite rare kernel panic so once you haven’t upgraded to 10.15.6 yet and are using VMware Fusion as the desktop virtualization tool of your choice, you shouldn’t update macOS yet.
Unfortunately, there’s not much else VMware can do at this point. “We have not yet identified any workaround other than refraining from installing macOS 10.15.6, which is a bit painful (and the advice will come too late for anyone who finds this thread because they are already running into this problem), or shutting down your VMs whenever you aren’t using them and rebooting your host every day or every few hours or every hour, which is … ugggggh,” said a VMware-engineer named Darius in the forums.
Although the problem can be narrowed down to a regression in the com.apple.security.sandbox-kext (or one of its related components) included in macOS 10.15.6 (19G73), there isn’t any workaround yet so far and disabling 3D-acceleration doesn’t help either. Additionally, VMware is not the only vendor of desktop virtualization software having problems as the problem is also told to affect Oracle’s VirtualBox as well, mostly with Windows 10 running as a guest-system.
It’s quite surprising that this effect didn’t appear in the beta-stages of the latest macOS-release but it is also measurable that Apple may need to tighten and improve its quality management in the software-sector a little bit. With each update there is another effect which either affects the Pro-users, tools like Carbon Copy Cloner or — in this case — virtualization tools. It definitely looks like Apple is far from done with macOS Catalina at the time of writing.
As of August 13th, 2020, this issue is fixed by the macOS Catalina 10.15.6 Supplemental Update Apple released this day!