Out-of-bounds read in Linux kernel - CVE-2026-63938
Published: July 20, 2026
Vulnerability identifier: #VU138708
CSH Severity: Low
CVSS v4.0: 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/E:U/U:Clear
CVE-ID: CVE-2026-63938
CWE-ID: CWE-125
Exploitation vector: Local access
Exploit availability:
No public exploit available
Vendor: Linux Foundation
Affected software:
Linux kernel
Linux kernel
Detailed vulnerability description
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.
How to mitigate CVE-2026-63938
Install security update from vendor's repository.