The prepare_vmcs02 function in arch/x86/kvm/vmx.c in the Linux kernel through 4.13.3 does not ensure that the CR8-load exiting and CR8-store exiting L0 vmcs02 controls exist in cases where L1 omits the use TPR shadow vmcs12 control, which allows KVM L2 guest OS users to obtain read and write access to the hardware CR8 register. https://nvd.nist.gov/vuln/detail/CVE-2017-12154
