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security announce CVE-2016-6259

Xen: denial of service via Intel SMAP

Synthesis of the vulnerability

An attacker, who is in a guest system on a Intel processor with SMAP can trigger a denial of service on the Xen host system.
Severity of this alert: 1/4.
Creation date: 26/07/2016.
Références of this alert: CTX214954, CVE-2016-6259, FEDORA-2016-0049aa6e5d, FEDORA-2016-01cc766201, openSUSE-SU-2016:2494-1, SUSE-SU-2016:2093-1, SUSE-SU-2016:2473-1, VIGILANCE-VUL-20225, XSA-183.
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Description of the vulnerability

The Xen product can be installed on an Intel processor (Broadwell or later) supporting SMAP (Supervisor Mode Access Prevention).

However, the compat_create_bounce_frame() function does not whistelist its userspace accesses, which generates a fatal error.

An attacker, who is in a guest system on a Intel processor with SMAP can therefore trigger a denial of service on the Xen host system.
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This threat impacts software or systems such as XenServer, Fedora, openSUSE Leap, SUSE Linux Enterprise Desktop, SLES, Xen.

Our Vigil@nce team determined that the severity of this computer threat 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 cybersecurity 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 Intel SMAP.
A patch is available:
  http://xenbits.xen.org/xsa/xsa183-unstable.patch
  http://xenbits.xen.org/xsa/xsa183-4.6.patch

Citrix XenServer: patch.
A patch is available:
  Citrix XenServer 7.0: CTX214992 - https://support.citrix.com/article/CTX214992
  Citrix XenServer 6.5 SP1: CTX214991 - https://support.citrix.com/article/CTX214991
  Citrix XenServer 6.2 SP1: CTX214990 - https://support.citrix.com/article/CTX214990
  Citrix XenServer 6.1: CTX214989 - https://support.citrix.com/article/CTX214989
  Citrix XenServer 6.0.2: CTX214987 - https://support.citrix.com/article/CTX2149867
  Citrix XenServer 6.0.2 Common Criteria: CTX214988 - https://support.citrix.com/article/CTX214988
  Citrix XenServer 6.0: CTX214986 - https://support.citrix.com/article/CTX214986

Fedora: new xen packages.
New packages are available:
  Fedora 23: xen 4.5.3-9.fc23
  Fedora 24: xen 4.6.3-4.fc24

openSUSE Leap 42.1: new xen packages (12/10/2016).
New packages are available:
  openSUSE Leap 42.1: xen 4.5.3_10-15.2

SUSE LE 12 SP1: new xen packages (07/10/2016).
New packages are available:
  SUSE LE 12 SP1: xen 4.5.3_10-20.1

SUSE LE 12 SP1: new xen packages (18/08/2016).
New packages are available:
  SUSE LE 12 SP1: xen 4.5.3_08-17.1
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