The Linux kernel vulnerability CVE-2026-64310 concerns the crypto CCP subsystem's handling of SEV ioctls. Previously, when SEV initialization failed, the code path could zero out the MSR_VM_HSAVE_PA register globally if triggered by userspace via /dev/sev ioctls such as SEV_PDH_GEN. This could cause a general protection fault and crash the host during subsequent VM execution. The patch changes the initialization logic to skip SNP initialization for ioctls that only require SEV firmware, preventing the clearing of HSAVE_PA. It also improves error reporting by surfacing the actual firmware error instead of masking it with a generic error code. The shutdown sequence was confirmed safe even if SNP was not initialized.

If exploited, this vulnerability could cause a host system crash due to a general protection fault triggered by improper clearing of a critical CPU register (MSR_VM_HSAVE_PA) during VM execution. This impacts system stability and availability but does not indicate direct code execution or data compromise from the provided information.

A fix has been implemented in the Linux kernel to address this vulnerability by modifying the SEV ioctl initialization process to avoid unnecessary SNP initialization and prevent clearing of the MSR_VM_HSAVE_PA register. Users should update to the fixed Linux kernel version containing this patch. Since no vendor advisory or patch links are provided, check the official Linux kernel repositories or vendor advisories for the specific patch and update instructions.