FreeBSD : xen-kernel -- CR0.TS and CR0.EM not always honored for x86 HVM guests (4d7cf654-ba4d-11e6-ae1b-002590263bf5)

This script is Copyright (C) 2016 Tenable Network Security, Inc.


Synopsis :

The remote FreeBSD host is missing a security-related update.

Description :

The Xen Project reports :

Instructions touching FPU, MMX, or XMM registers are required to raise
a Device Not Available Exception (#NM) when either CR0.EM or CR0.TS
are set. (Their AVX or AVX-512 extensions would consider only CR0.TS.)
While during normal operation this is ensured by the hardware, if a
guest modifies instructions while the hypervisor is preparing to
emulate them, the #NM delivery could be missed.

Guest code in one task may thus (unintentionally or maliciously) read
or modify register state belonging to another task in the same VM.

A malicious unprivileged guest user may be able to obtain or corrupt
sensitive information (including cryptographic material) in other
programs in the same guest.

See also :

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=214936
https://xenbits.xen.org/xsa/advisory-190.html
http://www.nessus.org/u?cb9c511e

Solution :

Update the affected package.

Risk factor :

Low / CVSS Base Score : 3.3
(CVSS2#AV:L/AC:M/Au:N/C:P/I:P/A:N)

Family: FreeBSD Local Security Checks

Nessus Plugin ID: 95504 ()

Bugtraq ID:

CVE ID: CVE-2016-7777

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