CVE-2026-81627
Qemu-kvm: vapic writable rom alias can escape the option-rom window and expose locked smram
A flaw was found in QEMU. The VAPIC setup hypercall in hw/i386/vapic.c does not validate that the writable RAM alias remains within the option ROM window. A privileged guest user on a Q35/KVM machine can position this alias over locked SMRAM, bypassing chipset D_LCK protection and injecting code into System Management Mode memory.
Fixes and workarounds
Workaround
The VAPIC TPR optimization can be disabled by preventing the kvmvapic option ROM from loading. When using libvirt, set the following in the guest's domain XML: ``` <features> <apic/> <hyperv> <vapic state='off'/> </hyperv> </features> ``` When using QEMU directly, pass `-global kvmvapic.rom=off` on the command line. This optimization is only used by 32-bit Windows guests for MMIO-based TPR register access. Linux guests, 64-bit Windows guests, and any guest using x2APIC or MSR-based TPR access are unaffected by disabling it.
Source: CNA: redhatAffected products and versions
| Product | Versions | Authority |
|---|---|---|
| Red Hat Enterprise Linux 10 Red Hat qemu-kvm
https://access.redhat.com/downloads/content/package-browser/ |
Range not reported
Other versions: affected |
CNA: redhat |
| Red Hat Enterprise Linux 6 Red Hat qemu-kvm
https://access.redhat.com/downloads/content/package-browser/ |
Range not reported
Other versions: unaffected |
CNA: redhat |
| Red Hat Enterprise Linux 7 Red Hat qemu-kvm
https://access.redhat.com/downloads/content/package-browser/ |
Range not reported
Other versions: affected |
CNA: redhat |
| Red Hat Enterprise Linux 7 Red Hat qemu-kvm-ma
https://access.redhat.com/downloads/content/package-browser/ |
Range not reported
Other versions: affected |
CNA: redhat |
| Red Hat Enterprise Linux 8 Red Hat virt-devel:rhel/qemu-kvm
https://access.redhat.com/downloads/content/package-browser/ |
Range not reported
Other versions: affected |
CNA: redhat |
| Red Hat Enterprise Linux 8 Red Hat virt:rhel/qemu-kvm
https://access.redhat.com/downloads/content/package-browser/ |
Range not reported
Other versions: affected |
CNA: redhat |
| Red Hat Enterprise Linux 9 Red Hat qemu-kvm
https://access.redhat.com/downloads/content/package-browser/ |
Range not reported
Other versions: affected |
CNA: redhat |
| Red Hat Enterprise Linux for NVIDIA 26 Red Hat qemu-kvm
https://access.redhat.com/downloads/content/package-browser/ |
Range not reported
Other versions: unknown |
CNA: redhat |
| Red Hat OpenShift Container Platform 4 Red Hat openshift/ose-rhel-coreos-8
https://access.redhat.com/downloads/content/package-browser/ |
Range not reported
Other versions: affected |
CNA: redhat |
| Red Hat OpenShift Container Platform 4 Red Hat openshift/ose-rhel-coreos-9
https://access.redhat.com/downloads/content/package-browser/ |
Range not reported
Other versions: affected |
CNA: redhat |
| Red Hat OpenShift Container Platform 5 Red Hat openshift/ose-rhel-coreos-9
https://access.redhat.com/downloads/content/package-browser/ |
Range not reported
Other versions: affected |
CNA: redhat |
| Red Hat OpenStack Platform 13 (Queens) Red Hat qemu-kvm-rhev
https://access.redhat.com/downloads/content/package-browser/ |
Range not reported
Other versions: affected |
CNA: redhat |
Version ranges are source assertions. Check the vendor advisory and your installed configuration before determining exposure.
CVSS assessments
| Version / score | Vector | Authority |
|---|---|---|
| 3.1 / 8.2 high |
CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H | CNA: redhat |
Exploit evidence
- https://gitlab.com/qemu-project/qemu/-/work_items/4206
exploit · ADP: CISA-ADP
References
- https://access.redhat.com/security/cve/CVE-2026-81627CNA: redhat · vdb-entry, x_refsource_REDHAT
- https://bugzilla.redhat.com/show_bug.cgi?id=2536950CNA: redhat · issue-tracking, x_refsource_REDHAT
- https://gitlab.com/qemu-project/qemu/-/work_items/4206CNA: redhat
- https://gitlab.com/qemu-project/qemu/-/work_items/4206ADP: CISA-ADP · exploit
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