The Linux kernel vulnerability CVE-2026-64307 concerns the crypto CCP driver and its handling of SNP initialization via the ioctl(SNP_CONFIG) interface. Previously, if SNP initialization failed, the ioctl could transparently retry initialization, potentially zeroing out MSR_VM_HSAVE_PA globally. This could cause a general protection fault and crash the host when running VMs under KVM. The patch refuses to retry initialization if SNP is not already initialized, preventing this unsafe state. The fix is an ABI break but targets a rare corner case. Additional mitigation options include refusing initialization if KVM is loaded or checking CPU HSAVE_PA before re-initializing.

If exploited, this vulnerability could cause a general protection fault leading to a host crash when running virtual machines under KVM. This impacts system stability and availability but does not indicate direct privilege escalation or data compromise from the provided information.

A fix has been implemented in the Linux kernel to refuse SNP re-initialization if it is not already initialized, preventing the unsafe retry behavior. Users should apply the official kernel update that includes this patch. Since this is an ABI break, users should be aware of potential compatibility issues. No additional vendor advisory or patch links are provided; check the Linux kernel release notes for the relevant update. No known exploits are reported in the wild.