Debian: DSA-3729-1 Moderate: Xen Hypervisor Fixes and Threat Mitigation

CVE-2016-7777 (XSA-190)

Jan Beulich from SUSE discovered that Xen does not properly honor
CR0.TS and CR0.EM for x86 HVM guests, potentially allowing guest
users to read or modify FPU, MMX, or XMM register state information
belonging to arbitrary tasks on the guest by modifying an
instruction while the hypervisor is preparing to emulate it.

CVE-2016-9379, CVE-2016-9380 (XSA-198)

Daniel Richman and Gabor Szarka of the Cambridge University
Student-Run Computing Facility discovered that pygrub, the boot
loader emulator, fails to quote (or sanity check) its results when
reporting them to its caller. A malicious guest administrator can
take advantage of this flaw to cause an information leak or denial
of service.

CVE-2016-9382 (XSA-192)

Jan Beulich of SUSE discovered that Xen does not properly handle x86
task switches to VM86 mode. A unprivileged guest process can take
advantage of this flaw to crash the guest or, escalate its
privileges to that ...