CVE-2026-98471: KVM: SEV: Do cache maintenance on the source VM during intra-host migration
In the Linux kernel, the following vulnerability has been resolved:
KVM: SEV: Do cache maintenance on the source VM during intra-host migration
Manually perform cache maintenance on the source VM during intra-host migration to ensure no stale data is left in CPU caches after the VM is destroyed. Because the source VM is "converted" to a non-SEV VM, KVM's memory reclaim flows won't trigger cache maintenance, e.g. when all guest memory is reclaimed in response to detaching from the mmunotifier.
Note, relying on the destination VM to do cache maintenance isn't an option as KVM doesn't require identical guest memory configurations, i.e. the source VM may have access to memory that the destination VM does not. Enforcing equivalent memory configurations is infeasible, as it would require a deep comparison of memslots, e.g. to verify that not only are the memslot identical, but what the memslots point at is also identical.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
ubuntu/linux-hwe-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-42.42~24.04.1 - Upgrade
Upgrade
ubuntu/linux-riscv-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-42.42.1~24.04.1 - Upgrade
Upgrade
ubuntu/linuxto a version that resolves this vulnerability.Fixed in 7.0.0-42.42 - Upgrade
Upgrade
ubuntu/linux-awsto a version that resolves this vulnerability.Fixed in 7.0.0-1016.17 - Upgrade
Upgrade
ubuntu/linux-gcpto a version that resolves this vulnerability.Fixed in 7.0.0-1016.18 - Upgrade
Upgrade
ubuntu/linux-ibmto a version that resolves this vulnerability.Fixed in 7.0.0-1017.17 - Upgrade
Upgrade
ubuntu/linux-oem-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1017.17 - Upgrade
Upgrade
ubuntu/linux-oracleto a version that resolves this vulnerability.Fixed in 7.0.0-1015.16 - Upgrade
Upgrade
ubuntu/linux-riscvto a version that resolves this vulnerability.Fixed in 7.0.0-42.42.1 - Upgrade
Upgrade
linux/Kernelto a version that resolves this vulnerability.Fixed in 6.18.55 - Upgrade
Upgrade
linux/Kernelto a version that resolves this vulnerability.Fixed in 7.2.9 - Compensating control
During intra-host migration of KVM SEV VMs, manually perform cache maintenance on the source VM before it is destroyed to ensure no stale data remains in CPU caches.
Event History
Frequently Asked Questions
Which systems are exposed to this issue?
Systems using KVM with AMD SEV guests and performing intra-host migration are exposed. The issue concerns source VMs that are converted to non-SEV VMs during that migration flow.
What condition leads to stale data remaining in CPU caches?
The condition occurs when guest memory on the source VM is reclaimed after the source has been converted to a non-SEV VM. In that state, KVM's normal memory-reclaim paths do not trigger the needed cache maintenance.
Can cache maintenance be delegated to the destination VM?
No. KVM does not require the source and destination guests to have identical memory configurations, so the source may access memory that is not available to the destination.