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CVE-2026-98718: KVM: SEV: Do cache maintenance on the source VM *before* clearing SEV state

• Severity: unknown
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-10-18 · updated 2026-10-19

Description

In the Linux kernel, the following vulnerability has been resolved: KVM: SEV: Do cache maintenance on the source VM *before* clearing SEV state Explicitly flush caches after intra-host migration before clearing "SEV active" on the source VM, as doing cache maintenance afterwards creates a tiny window where memory reclaim could return memory to the host without performing a cache flush, e.g. as pointed out by Sashiko: CPU1 in sev_migrate_from(): src->active = false; CPU2 running concurrent unmap: Since active is false, the automatic cache flush in sev_guest_memory_reclaimed is skipped. The host frees and reallocates the page. CPU1 in sev_migrate_from(): sev_writeback_caches(src_kvm); Executes a hardware cache flush (wbnoinvd), which writes the guest's old dirty ciphertext over the new page owner's data.

Affected products

• Linux kernel: from 6.18.55 before 6.18.56; from 7.2.9 before 7.2.10 — fixed in 6.18.56, 7.2.10

How to fix

Upgrade to a fixed version: Linux kernel 6.18.56, 7.2.10. Check the vendor advisory for mitigations.

References

• https://git.kernel.org/stable/c/8b7d4f68fef96cebe0b6dbb6e5607772337f7369
• https://git.kernel.org/stable/c/973ea70393e885e540f714904e51bc6cac80e3d7
• https://git.kernel.org/stable/c/de83ff6a4d8f3618473bedb3c4400020c22e8a8a

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