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Vulnerability of Xen: information disclosure via HVM CR0.TS/EM

Synthesis of the vulnerability 

An attacker can use CR0.TS/EM on Xen x86 HVM, in order to obtain sensitive information on the current system.
Vulnerable systems: XenServer, Debian, Fedora, openSUSE, openSUSE Leap, SUSE Linux Enterprise Desktop, SLES, Xen.
Severity of this threat: 1/4.
Creation date: 04/10/2016.
Références of this weakness: CERTFR-2016-AVI-328, CTX217363, CVE-2016-7777, DLA-699-1, DSA-3729-1, FEDORA-2016-4c407cd849, FEDORA-2016-689f240960, openSUSE-SU-2016:3134-1, openSUSE-SU-2017:0007-1, openSUSE-SU-2017:0008-1, SUSE-SU-2016:3044-1, SUSE-SU-2016:3067-1, SUSE-SU-2016:3083-1, SUSE-SU-2016:3156-1, SUSE-SU-2016:3174-1, SUSE-SU-2016:3273-1, VIGILANCE-VUL-20762, XSA-190.

Description of the vulnerability 

The Xen product can manage x86 HVM guest systems.

However, an attacker can raise a Device Not Available Exception while CR0.EM or CR0.TS are set, which can be used to read a register of another task on the same VM.

An attacker can therefore use CR0.TS/EM on Xen x86 HVM, in order to obtain sensitive information on the current system.
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This computer threat alert impacts software or systems such as XenServer, Debian, Fedora, openSUSE, openSUSE Leap, SUSE Linux Enterprise Desktop, SLES, Xen.

Our Vigil@nce team determined that the severity of this weakness announce is low.

The trust level is of type confirmed by the editor, with an origin of user shell.

An attacker with a expert ability can exploit this computer weakness bulletin.

Solutions for this threat 

Xen: version 4.7.1.
The version 4.7.1 is fixed:
  https://xenbits.xenproject.org/gitweb/?p=xen.git;a=shortlog;h=refs/heads/stable-4.7

Xen: version 4.6.4.
The version 4.6.4 is fixed:
  https://xenbits.xenproject.org/gitweb/?p=xen.git;a=shortlog;h=refs/heads/stable-4.6

Xen: patch for HVM CR0.TS/EM.
A patch is available:
  http://xenbits.xen.org/xsa/xsa190.patch
  http://xenbits.xen.org/xsa/xsa190-4.5.patch
  http://xenbits.xen.org/xsa/xsa190-4.6.patch

Citrix XenServer: patch for HVM CR0.TS/EM.
A patch is indicated in information sources.

Debian 7: new xen packages.
New packages are available:
  Debian 7: xen 4.1.6.lts1-3

Debian 8: new xen packages.
New packages are available:
  Debian 8: xen 4.4.1-9+deb8u8

Fedora: new xen packages.
New packages are available:
  Fedora 23: xen 4.5.5-2.fc23
  Fedora 24: xen 4.6.3-6.fc24

openSUSE 13.2: new xen packages.
New packages are available:
  openSUSE 13.2: xen 4.4.4_06-58.1

openSUSE Leap 42.1: new xen packages.
New packages are available:
  openSUSE Leap 42.1: xen 4.5.5_06-18.1

openSUSE Leap: new xen packages.
New packages are available:
  openSUSE Leap 42.2: xen 4.7.1_02-3.1

SUSE LE 11 SP2: new xen packages.
New packages are available:
  SUSE LE 11 SP2: xen 4.1.6_08-32.1

SUSE LE 11 SP3: new xen packages.
New packages are available:
  SUSE LE 11 SP3: xen 4.2.5_21-30.1

SUSE LE 11 SP4: new xen packages.
New packages are available:
  SUSE LE 11 SP4: xen 4.4.4_10-43.5

SUSE LE 12: new xen packages.
New packages are available:
  SUSE LE 12 SP2: xen 4.7.1_02-25.1
  SUSE LE 12 SP1: xen 4.5.5_02-22.3.1

SUSE LE 12 RTM: new xen packages.
New packages are available:
  SUSE LE 12 RTM: xen 4.4.4_05-22.25.1
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