Bug 2554844 (CVE-2026-98471)

Summary: CVE-2026-98471 kernel: KVM: SEV: Do cache maintenance on the source VM during intra-host migration
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: akhatavk, aos-team-art-private, asdas, dpaolell, jdelft, jupierce, lgarciaa, mbiarnes, ppalepu, ppostler, prdhamdh, rhel-process-autobot, sghai, sidsharm, suppawar, vlaad, watson-tool-maintainers
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's KVM (Kernel-based Virtual Machine) subsystem for AMD SEV (Secure Encrypted Virtualization). During intra-host migration of an encrypted virtual machine, the source virtual machine's CPU caches are not properly flushed before the system reclaims its memory. A local attacker could exploit this issue to read residual data remaining in the processor cache, leading to an information disclosure of sensitive guest memory.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Description OSIDB Bzimport 2026-10-18 15:22:28 UTC 
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 mmu_notifier.

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.
Comment 1 Mauro Matteo Cascella 2026-10-20 08:54:10 UTC 
Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-98471.mbox