KVM Vulnerability in Linux Kernel Affecting Virtual Machine Operations

CVE-2026-43265

What is CVE-2026-43265?

The vulnerability in the Linux kernel KVM component arises from improper handling of blocked virtual CPUs (vCPUs) when nested events are present. Upon transitioning to userspace from a blocking state, a spurious exit can occur—often manifesting as KVM_EXIT_UNKNOWN—potentially jeopardizing the stability of the virtual machine (VM). Although it's intended that a vCPU does not enter a blocking state with already injected events, user space manipulations can create scenarios where this rule is violated, leading to undefined behavior. The resolution aims to mitigate the risk of such situations, allowing the VM to function more reliably despite underlying complexities.

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