CVE-2026-63940: KVM: SEV: Ignore Port I/O requests of length '0'

highCVSS 7.7CVE-2026-63940

CSIRTS triage

Other

What: A fix has been made to ignore Port I/O requests of length '0' in KVM SEV.
Who is affected: Deployments using KVM with SEV enabled.
Urgency: Remediation is high urgency due to the potential for exploitation.
Action: Update to the latest KVM version.

AI-assisted analysis generated from the source advisory — verify against the original.

Details

Source: Microsoft Security Response Center (INTL · vendor-psirt · site)
Severity: high — CVSS 7.7
Published: 2026-07-14
Exploitation: Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-63940

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Low exploitation riskCVE-2026-639400.18% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 8% of all EPSS-scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-63940	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

unknownMultiple vulnerabilities in SUSE Linux kernel (August 28, 2026)cert-fr-avis
unknownUSN-8664-1: Linux kernel (NVIDIA BaseOS) vulnerabilitiesubuntu
unknownUSN-8663-1: Linux kernel (NVIDIA) vulnerabilitiesubuntu
highUSN-8618-1: Linux kernel vulnerabilitiesubuntu
highUSN-8603-1: Linux kernel (Azure) vulnerabilitiesubuntu
highUSN-8593-1: Linux kernel vulnerabilitiesubuntu
criticalCVE-2026-63940: In the Linux kernel, the following vulnerability has been resolved: KVM: SEV: Ignore Port I/O …nvd

Recent advisories for KVM

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

unknownCVE-2026-80699: In the Linux kernel, the following vulnerability has been resolved: KVM: arm64: vgic: Avoid do…nvd · 2026-08-28
criticalCVE-2026-80684: In the Linux kernel, the following vulnerability has been resolved: KVM: s390: pci: Fix NULL d…nvd · 2026-08-28
highCVE-2026-80665: In the Linux kernel, the following vulnerability has been resolved: KVM: arm64: nv: Inject SEA…nvd · 2026-08-28
highCVE-2026-74607: In the Linux kernel, the following vulnerability has been resolved: KVM: SVM: Serialize access…nvd · 2026-08-22
unknownUSN-8667-1: Linux kernel (KVM) vulnerabilitiesubuntu · 2026-08-21
criticalCVE-2026-74568: In the Linux kernel, the following vulnerability has been resolved: KVM: arm64: vgic: Fix race…nvd · 2026-08-15