Late cache flush in Linux KVM SEV migration corrupts reused pages
Key facts
- Attack vector
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- Privileges required
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- User interaction
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- Attack complexity
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- Impact type
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- Confidentiality · integrity · availability
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- Fix status
- Partial Red Hat: 5 without a fix
No CVSS vector from any source. Fix status from CNA and Red Hat.
Summary
The Linux kernel from 6.18.55 before 6.18.56 and from 7.2.9 before 7.2.10 has a flaw in KVM SEV intra-host migration. The source VM's cache flush runs after its SEV active state is cleared, so a concurrent memory reclaim can return a page to the host without a flush. Stale dirty guest ciphertext can then be written over the data of the page's new owner.
Written with Claude Haiku 5.5 from the sources below · 2026-11-06
Description from the CNA
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.
Why it matters now
SSVC decision points
Not available: CISA has not published SSVC decision points for this record.
Affected products
Remediation
Update the Linux kernel to 6.18.56 or to 7.2.10. Red Hat lists Red Hat Enterprise Linux 8, 9 and 10 and Red Hat OpenShift Container Platform 4 and 5 as affected without a fix, with plan none available.
Written with Claude Haiku 5.5 from the sources below · 2026-11-06
- Fix · CNA Linux (Linux) Fixed in 6.18.56, 7.2.10
Vendor assessments
Red Hat
Red Hat rating: Important. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Red Hat Enterprise Linux 10 | Affected | No fix yet |
| Red Hat Enterprise Linux 8 | Affected | No fix yet |
| Red Hat Enterprise Linux 9 | Affected | No fix yet |
| Red Hat OpenShift Container Platform 4 | Affected | No fix yet |
| Red Hat OpenShift Container Platform 5 | Affected | No fix yet |
Not affected: 2 products
- Red Hat Enterprise Linux 6
- Red Hat Enterprise Linux 7
Timeline
- 2026-10-18 Threatist record created from CVE-2026-98718
- 2026-10-18 Alias added: GHSA-8j5c-4j8r-8m5m
- 2026-10-19 Affected versions changed · CNA
- 2026-10-23 Affected versions changed · Red Hat
- 2026-10-23 CVSS score added · Red Hat
- 2026-11-04 Affected versions changed · Red Hat
References
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Sources
- CVE-2026-98718 · CVE Program
- CVE-2026-98718 · NVD
- FIRST EPSS
- GHSA-8j5c-4j8r-8m5m · GitHub Advisory Database · CC BY 4.0
- CVE-2026-98718 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences