PT-2026-29484 · Linux · Linux

Published

2026-04-01

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Updated

2026-04-01

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CVE-2026-23401

None

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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: 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 ---[ end trace 0000000000000000 ]---

Related Identifiers

CVE-2026-23401

Affected Products

Linux