The virtual machine escape demonstrated at Pwn2Own this year showed that for even as isolated software defined machines, VMs are not without there security concerns. Andrea Mauro took this as inspiration to reflect on some of the other vulnerabilities. Virtually networking is probably the most common, as the guest machines as vulnerable as any other to these kind of exploits. These are mitigated by the supposed isolation each machine enjoys. Andrea does point out though that any time you have shared components between machines, you introduce the possibility of mitigating the virtual machines inherent estrangement.
It goes to show that the old tradeoff of security vs convenience applies equally as well to the virtual machine world as to the physical one.
Andrea Mauro comments:
Recent VMware security bug (VMSA-2017-0006) is related to one of the worst possible security issue in a virtualization environment: a possible “guest escape” vulnerability that allows arbitrary code execution on a host system from the guest system. It’s not the first time of a similar risk (see, for example, Microsoft Edge used to escape VMware Workstation at Pwn2Own 2017) but this kind of issue is a different risk level if it affect Worksation (so “just” a client environment) or a ESXi (potentially a datacenter environment).
Read more at: How a VM is really isolated