The vulnerability in the Linux kernel's KVM arm64 nested virtualization code stemmed from improper restoration of the SPSR_EL2 register in the kvm_hyp_handle_mops() function. This function resets the single-step state machine by modifying vcpu_cpsr() and writing the result to hardware. However, in nested virtualization, vcpu_cpsr() is a synthetic value requiring translation before hardware write, which was missing. The fix involves directly modifying SPSR_EL2 and avoiding the synthetic state, ensuring correct state synchronization on the next full exit to KVM.

This vulnerability affects nested virtualization on arm64 KVM, potentially allowing an attacker with low privileges to cause a state corruption leading to confidentiality, integrity, and availability impacts (as indicated by the CVSS vector: high impact on confidentiality, integrity, and availability).

A fix for this vulnerability has been implemented in the Linux kernel. Users should update to the fixed kernel version once available. Patch status is not yet confirmed in the provided data; check the official Linux kernel advisories for the exact fixed versions and remediation guidance.