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Vulnerability of Xen: denial of service via timers

Synthesis of the vulnerability 

An attacker, inside a guest system, can trigger a fatal error via Xen timers, in order to trigger a denial of service on the host system.
Impacted products: XenServer, Debian, Fedora, openSUSE Leap, SUSE Linux Enterprise Desktop, SLES, Xen.
Severity of this bulletin: 1/4.
Creation date: 22/09/2020.
Références of this threat: CERTFR-2020-AVI-593, CERTFR-2020-AVI-594, CTX282314, CVE-2020-25604, DSA-4769-1, FEDORA-2020-d46fe34349, FEDORA-2020-f668e579be, openSUSE-SU-2020:1608-1, SUSE-SU-2020:14521-1, SUSE-SU-2020:2786-1, SUSE-SU-2020:2787-1, SUSE-SU-2020:2788-1, SUSE-SU-2020:2789-1, SUSE-SU-2020:2790-1, SUSE-SU-2020:2791-1, SUSE-SU-2020:2822-1, VIGILANCE-VUL-33387, XSA-336.

Description of the vulnerability 

An attacker, inside a guest system, can trigger a fatal error via Xen timers, in order to trigger a denial of service on the host system.
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This computer vulnerability alert impacts software or systems such as XenServer, Debian, Fedora, openSUSE Leap, SUSE Linux Enterprise Desktop, SLES, Xen.

Our Vigil@nce team determined that the severity of this computer threat alert 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 security vulnerability.

Solutions for this threat 

Xen: patch for timers.
A patch is available:
  http://xenbits.xen.org/xsa/xsa336-4.11.patch
  http://xenbits.xen.org/xsa/xsa336.patch

Citrix Hypervisor, XenServer: patch.
A patch is available:
  Citrix Hypervisor 8.2 LTSR: XS82E007: https://support.citrix.com/article/CTX283446
  Citrix Hypervisor 8.1: XS81E009: https://support.citrix.com/article/CTX283445
  Citrix XenServer 7.1 LTSR CU2: XS71ECU2047: https://support.citrix.com/article/CTX283444
  Citrix XenServer 7.0: XS70E083: https://support.citrix.com/article/CTX283443

Debian 10: new xen packages.
New packages are available:
  Debian 10: xen 4.11.4+37-g3263f257ca-1

Fedora 31: new xen packages.
New packages are available:
  Fedora 31: xen 4.12.3-5.fc31

Fedora 32: new xen packages.
New packages are available:
  Fedora 32: xen 4.13.1-6.fc32

openSUSE Leap 15.2: new xen packages.
New packages are available:
  openSUSE Leap 15.2: xen 4.13.1_08-lp152.2.9.1

SUSE LE 11 SP4: new xen packages.
New packages are available:
  SUSE LE 11 SP4: xen 4.4.4_44-61.55.1

SUSE LE 12 SP2: new xen packages.
New packages are available:
  SUSE LE 12 SP2: xen 4.7.6_10-43.67.1

SUSE LE: new xen packages.
New packages are available:
  SUSE LE 12 SP3: xen 4.9.4_12-3.74.1
  SUSE LE 12 SP4: xen 4.11.4_08-2.36.1
  SUSE LE 12 SP5: xen 4.12.3_08-3.24.1
  SUSE LE 15 RTM: xen 4.10.4_16-3.41.1
  SUSE LE 15 SP1: xen 4.12.3_08-3.28.1
  SUSE LE 15 SP2: xen 4.13.1_08-3.10.1
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