KVM Vulnerability in Linux Kernel Exposes Users to TSC Scaling Threats

CVE-2023-53663

What is CVE-2023-53663?

A vulnerability in the Linux kernel's KVM (Kernel-based Virtual Machine) allows users to bypass checks on nested TSC (Timestamp Counter) scaling support. Instead of verifying TSC scaling, the implementation mistakenly asserts that the feature is exposed to Level 1 (L1) when there's a mismatch with KVM's default MSR_AMD64_TSC_RATIO. This flaw can be exploited by manipulating the MSR and modifying the guest CPUID, potentially leading to a denial of service through continuous warnings and CPU errors. The vulnerability arises particularly within the nested virtualization context, where improper assumptions about feature exposure could compromise the system.

References