Xen warns AMD Zen 2 opcode cache flaw can enable guest-to-host escalation

Xen disclosed Xen Security Advisory 490 for CVE-2025-54518, an x86 CPU opcode cache corruption flaw affecting Xen deployments on certain AMD processors. The issue is believed to impact AMD Family 17h CPUs based on the Zen 2 microarchitecture, and Xen said successful exploitation could let code running at any privilege level gain higher privileges, including userspace-to-kernel and guest-to-host escalation.

The advisory says all Xen versions are affected when running on the vulnerable CPUs, while other AMD processors and CPUs from other vendors are not known to be impacted. Xen reported that no mitigations are available and directed users to apply released patches for xen-unstable, Xen 4.21.x through 4.18.x, and Xen 4.17.x; the 4.17 branch also requires an unusual additional backported patch because the fix is closely coupled with an earlier change.