Time-of-check Time-of-use (TOCTOU) Race Condition in Linux kernel - CVE-2026-63937
Published: July 20, 2026
Vulnerability identifier: #VU138707
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-2026-63937
CWE-ID: CWE-367
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 time-of-check time-of-use race condition in the KVM SEV Page State Change buffer handling in arch/x86/kvm/svm/sev.c when processing guest-accessible PSC buffer entries and indices. A local user can modify buffer values during processing to cause a denial of service.
The issue involves guest-accessible PSC buffer header fields and entries used for validation and array indexing.
How to mitigate CVE-2026-63937
Install security update from vendor's repository.