CVE-2026-45987
MediumCVSS 5.5Exploitation Probability (EPSS)
Low risk7th percentile - higher than 7% of all known CVEs
Summary
A vulnerability has been identified in the Linux kernel related to KVM, concerning the synchronization of interrupt state in nested virtual machines. The issue arises when KVM_SET_VCPU_EVENTS is called before KVM_SET_NESTED_STATE, potentially leading to a hang of the vCPU in L2.
Risk Assessment
This vulnerability may result in the hanging of the L2 virtual machine, impacting the availability of services running on that machine. This can be particularly problematic in production environments.
Recommendation
It is recommended to update the Linux kernel to a version where this vulnerability has been fixed to ensure proper synchronization of interrupt state in nested virtual machines.
Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: KVM: nSVM: Sync interrupt shadow to cached vmcb12 after VMRUN of L2 After VMRUN in guest mode, nested_sync_control_from_vmcb02() syncs fields written by the CPU from vmcb02 to the cached vmcb12. This is because the cached vmcb12 is used as the authoritative copy of some of the controls, and is the payload when saving/restoring nested state. int_state is also written by the CPU, specifically bit 0 (i.e. SVM_INTERRUPT_SHADOW_MASK) for nested VMs, but it is not sync'd to cached vmcb12. This does not cause a problem if KVM_SET_NESTED_STATE preceeds KVM_SET_VCPU_EVENTS in the restore path, as an interrupt shadow would be correctly restored to vmcb02 (KVM_SET_VCPU_EVENTS overwrites what KVM_SET_NESTED_STATE restored in int_state). However, if KVM_SET_VCPU_EVENTS preceeds KVM_SET_NESTED_STATE, an interrupt shadow would be restored into vmcb01 instead of vmcb02. This would mostly be benign for L1 (delays an interrupt), but not for L2. For L2, the vCPU could hang (e.g. if a wakeup interrupt is delivered before a HLT that should have been in an interrupt shadow). Sync int_state to the cached vmcb12 in nested_sync_control_from_vmcb02() to avoid this problem. With that, KVM_SET_NESTED_STATE restores the correct interrupt shadow state, and if KVM_SET_VCPU_EVENTS follows it would overwrite it with the same value.