CVE-2026-23401

Summary

In the Linux kernel, the following vulnerability has been resolved:

KVM: x86/mmu: Drop/zap existing present SPTE even when creating an MMIO SPTE

When installing an emulated MMIO SPTE, do so after dropping/zapping the existing SPTE (if it's shadow-present). While commit a54aa15c6bda3 was right about it being impossible to convert a shadow-present SPTE to an MMIO SPTE due to a guest write, it failed to account for writes to guest memory that are outside the scope of KVM.

E.g. if host userspace modifies a shadowed gPTE to switch from a memslot to emulted MMIO and then the guest hits a relevant page fault, KVM will install the MMIO SPTE without first zapping the shadow-present SPTE.

————[ cut here ]———— is_shadow_present_pte(*sptep) WARNING: arch/x86/kvm/mmu/mmu.c:484 at mark_mmio_spte+0xb2/0xc0 [kvm], CPU#0: vmx_ept_stale_r/4292 Modules linked in: kvm_intel kvm irqbypass CPU: 0 UID: 1000 PID: 4292 Comm: vmx_ept_stale_r Not tainted 7.0.0-rc2-eafebd2d2ab0-sink-vm #319 PREEMPT Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015 RIP: 0010:mark_mmio_spte+0xb2/0xc0 [kvm] Call Trace: <TASK> mmu_set_spte+0x237/0x440 [kvm] ept_page_fault+0x535/0x7f0 [kvm] kvm_mmu_do_page_fault+0xee/0x1f0 [kvm] kvm_mmu_page_fault+0x8d/0x620 [kvm] vmx_handle_exit+0x18c/0x5a0 [kvm_intel] kvm_arch_vcpu_ioctl_run+0xc55/0x1c20 [kvm] kvm_vcpu_ioctl+0x2d5/0x980 [kvm] __x64_sys_ioctl+0x8a/0xd0 do_syscall_64+0xb5/0x730 entry_SYSCALL_64_after_hwframe+0x4b/0x53 RIP: 0033:0x47fa3f </TASK> —[ end trace 0000000000000000 ]—

Affected Software

VendorProductVersion RangeStatus
LinuxLinuxa54aa15c6bda3ca7e2f9e040ba968a1da303e24f < 20656cd1f243d3a154aac5dd1b823110b6906fe1affected
LinuxLinuxa54aa15c6bda3ca7e2f9e040ba968a1da303e24f < ed5909992f344a7d3f4024261e9f751d9618a27daffected
LinuxLinuxa54aa15c6bda3ca7e2f9e040ba968a1da303e24f < fd28c5618699180cd69619801e9ae6a5266c0a22affected
LinuxLinuxa54aa15c6bda3ca7e2f9e040ba968a1da303e24f < 459158151a158a6703b49f3c9de0e536d8bd553faffected
LinuxLinuxa54aa15c6bda3ca7e2f9e040ba968a1da303e24f < 695320de6eadb75aaed8be1787c4ce4c189e4c7baffected
LinuxLinuxa54aa15c6bda3ca7e2f9e040ba968a1da303e24f < bce7fe59d43531623f3e43779127bfb33804925daffected
LinuxLinuxa54aa15c6bda3ca7e2f9e040ba968a1da303e24f < aad885e774966e97b675dfe928da164214a71605affected
LinuxLinux5.13affected
LinuxLinux0 < 5.13unaffected
LinuxLinux5.15.203 <= 5.15.*unaffected
LinuxLinux6.1.168 <= 6.1.*unaffected
LinuxLinux6.6.131 <= 6.6.*unaffected
LinuxLinux6.12.80 <= 6.12.*unaffected
LinuxLinux6.18.21 <= 6.18.*unaffected
LinuxLinux6.19.11 <= 6.19.*unaffected
LinuxLinux7.0 <= *unaffected

Weaknesses

ADP Enrichment

kernel: Linux kernel KVM: Privilege escalation or denial of service due to improper shadow page table entry handling

Additional References

References