Linux Kernel Vulnerability in KVM Affecting MMU Reset in Nested Virtual Machines

CVE-2026-99176

What is CVE-2026-99176?

A vulnerability within the Linux Kernel's KVM component can occur when loading the L2 state fails during a nested virtual machine operation. Specifically, if the vCPU's Memory Management Unit (MMU) pointer is not reset back to the root MMU, operations like emulating the RSM instruction or handling KVM_SET_NESTED_STATE could lead to using a nested MMU improperly. This situation can cause severe issues, including potential NULL pointer dereference errors, leading to crashes if the nested state is freed prematurely. Notably, the problem arises in scenarios where the nested EPT MMU structure is mismanaged, risking system stability and security.

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