Xen 4.0.x, 4.1.x, and 4.2.x does not properly restrict the contents of a XRSTOR, which allows local PV guest users to cause a denial of service (unhandled exception and hypervisor crash) via unspecified vectors.
Debian Linux Security Advisory 3006-1 - Multiple security issues have been discovered in the Xen virtualisation solution which may result in information leaks or denial of service.