An AMD SEV Secure Memory Encryption (SEV‑SNP) bug in the Linux kernel’s KVM implementation allows a privileged host process to trigger a kernel panic by replaying a previously encrypted virtual CPU state to the VMSA. The flaw causes a Required Memory Protection (RMP) page fault when the kernel attempts to sync the VMSA of a vCPU that has already been launched and encrypted. The resulting host crash delivers a denial‑of‑service to the underlying hypervisor and any workloads running there. The weakness relates to CWE‑821, highlighting flawed error handling and race conditions that bypass normal state‑synchronization safeguards.

Affected systems: Victims are Linux hosts running KVM with SEV‑SNP (or SEV‑ES) support enabled and using kernel versions that include the unpatched code. The issue was introduced in the commit ad73109ae7ec and persisted until the security release that incorporated the patch rejecting the sync operation. Any distribution or OEM that ships a kernel older than the patched release and permits SEV guests—such as many recent enterprise and cloud images—falls within scope. Host systems that do not enable SEV or for which SEV support has been disabled are not affected.

Risk and exploitability: The CVSS score of 5.5 indicates moderate severity, primarily because the flaw can cause host instability but does not grant data exfiltration or privilege escalation. The EPSS score of less than 1 % suggests a low probability of exploitation in the wild, and the vulnerability is not listed in the CISA KEV catalog. The attack requires local privileged access to the host, typically root or a user with the ability to issue KVM ioctl calls. An attacker could use a compromised QEMU instance or malicious guest to trigger the sync which, in turn, would cause an RMP page fault and a kernel panic, disrupting the hypervisor and all running virtual machines. Because the flaw is limited to hosts with SEV‑SNP support, the attack surface is comparatively narrow.