CVE-2026-63938

A flaw was found in the Linux kernel's Kernel-based Virtual Machine (KVM) Secure Encrypted Virtualization (SEV) feature. When processing Page State Change (PSC) requests, the system does not properly validate the PSC buffer against the effective size of the scratch area. This can occur if a guest operating system provides a pointer that is not precisely at the start of the Guest Hypervisor Communication Block (GHCB) shared buffer, potentially leading to out-of-bounds memory access. This vulnerability could allow a malicious guest to cause a denial of service on the host system.

This vulnerability is rated as Moderate impact because triggering the condition requires local administrative or privileged access within an AMD SEV-SNP confidential virtual machine. Systems that do not host confidential virtual machines on supported AMD processors are unaffected by this issue. While an exploit could destabilize the underlying host hypervisor, the risk does not extend to remote or non-virtualized enterprise environments.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Mitigation for this issue is either not available or the currently available options don't meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.