CVE-2026-63938: KVM: SEV: Check PSC request indices against the actual size of the buffer

Severity: critical (CVSS 9.3 v3.1)
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: 2026-07-19 · updated 2026-10-27
Weakness: CWE-125

Description

In the Linux kernel, the following vulnerability has been resolved: KVM: SEV: Check PSC request indices against the actual size of the buffer When processing Page State Change (PSC) requests, validate the PSC buffer against the effective size of the scratch area, which could be less than the maximum size if the guest provided a pointer that isn't exactly at the start of the GHCB shared buffer.

Affected products

Linux kernel: from 6.11 before 6.12.93; from 6.13 before 6.18.35; from 6.19 before 7.0.12; 7.1-rc1, 7.1-rc2, 7.1-rc3, 7.1-rc4, 7.1-rc5 — fixed in 6.12.93, 6.18.35, 7.0.12
Linux kernel: 6.11 — fixed in 7.1

How to fix

Upgrade to a fixed version: Linux kernel 6.12.93, 6.18.35, 7.0.12; Linux kernel 7.1. Check the vendor advisory for mitigations.

References

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