CVE-2026-89931: KVM: nVMX: Ensure KVM_REQ_GET_NESTED_STATE_PAGES is cleared on VM-Exit
In the Linux kernel, the following vulnerability has been resolved:
KVM: nVMX: Ensure KVMREQGETNESTEDSTATEPAGES is cleared on VM-Exit
Always check and clear KVMREQGETNESTEDSTATEPAGES when emulating a nested VM-Exit to ensure the request is cleared, even when KVM was built with CONFIGKVMHYPERV=n, as KVM subtly relies on the "check" to clear the flag and thus avoid double-mapping the vmcs12 pages, e.g. if KVM manages to bail from VM-Enter without processing the request, and then emulates VMLAUNCH or VMRESUME.
Affected Software
Event History
Frequently Asked Questions
Is this limited to KVM builds with Hyper-V support enabled?
No. The issue can occur even when KVM is built with CONFIG_KVM_HYPERV=n, because the request check is also relied on to clear the pending flag.
What condition can lead to the problematic state?
The risk arises when KVM exits VM-Enter before processing the nested-state-pages request and subsequently emulates VMLAUNCH or VMRESUME. In that sequence, the stale request can cause the vmcs12 pages to be mapped twice.