SB20260720292 - Out-of-bounds read in Linux kernel kvm svm

Description

This security bulletin contains information about 1 vulnerability.

1) Out-of-bounds read (CVE-ID: CVE-2026-63938)

CWE-ID: CWE-125 - Out-of-bounds read

CVSSv4: 6.8 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]

The vulnerability allows a local user to cause a denial of service.

The vulnerability exists due to an out-of-bounds read in the KVM SEV PSC request handling in arch/x86/kvm/svm/sev.c when processing Page State Change requests with indices that exceed the effective scratch buffer size. A local user can provide a crafted PSC buffer pointer and PSC indices to cause a denial of service.

The issue arises if the guest-provided pointer is not exactly at the start of the GHCB shared buffer, which can reduce the effective size of the scratch area.

Remediation

Install update from vendor's website.

References

• https://git.kernel.org/stable/c/121d88de56bc5c0ba0ce2f6381af67f948a7e7c1
• https://git.kernel.org/stable/c/505a3b94535583e4265360e2621734e355ef263d
• https://git.kernel.org/stable/c/5198f70c09a5f6e9e5f5a0a2c6b388f24294b176
• https://git.kernel.org/stable/c/75c8d1d7291268b479794fba5808971dc2f5eaf3