Heap-based buffer overflow in Linux kernel - CVE-2026-63939
Published: July 20, 2026
Vulnerability identifier: #VU138709
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-2026-63939
CWE-ID: CWE-122
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 a heap-based buffer overflow in the KVM SEV GHCB scratch area handling in arch/x86/kvm/svm/sev.c when processing PSC requests with a guest-provided scratch area pointer. A local user can provide a crafted scratch area pointer and length values to cause a denial of service.
The issue occurs when the scratch area is located in the GHCB shared buffer, where only the minimum header length was tracked instead of the full effective scratch area size.
How to mitigate CVE-2026-63939
Install security update from vendor's repository.