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Vulnerability of Xen: privilege escalation via IOMMU Read/write DMA Access

Synthesis of the vulnerability 

An attacker, inside a guest system, can bypass restrictions via IOMMU Read/write DMA Access of Xen, in order to escalate his privileges on the host system.
Impacted software: XenServer, Debian, SUSE Linux Enterprise Desktop, SLES, Xen.
Severity of this computer vulnerability: 2/4.
Creation date: 18/02/2021.
Références of this announce: CERTFR-2021-AVI-135, CERTFR-2021-AVI-460, CTX316324, CVE-2021-27379, DSA-4888-1, SUSE-SU-2021:1250-1, SUSE-SU-2021:1251-1, SUSE-SU-2021:1252-1, SUSE-SU-2021:1268-1, VIGILANCE-VUL-34612, XSA-366.

Description of the vulnerability 

An attacker, inside a guest system, can bypass restrictions via IOMMU Read/write DMA Access of Xen, in order to escalate his privileges on the host system.
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This weakness alert impacts software or systems such as XenServer, Debian, SUSE Linux Enterprise Desktop, SLES, Xen.

Our Vigil@nce team determined that the severity of this computer vulnerability note is medium.

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 bulletin.

Solutions for this threat 

Xen: patch for IOMMU Read/write DMA Access.
A patch is available:
  http://xenbits.xen.org/xsa/xsa366-4.11.patch

Citrix Hypervisor: patch.
A patch is available:
  Citrix Hypervisor 8.2 LTSR: CTX313807 https://support.citrix.com/article/CTX313807
  Citrix XenServer 7.1 LTSR CU2: CTX313806 https://support.citrix.com/article/CTX313806

Debian 10: new xen packages.
New packages are available:
  Debian 10: xen 4.11.4+99-g8bce4698f6-1

SUSE LE 12 SP2: new xen packages.
New packages are available:
  SUSE LE 12 SP2: xen 4.7.6_14-43.76.1

SUSE LE 12 SP3: new xen packages.
New packages are available:
  SUSE LE 12 SP3: xen 4.9.4_16-3.83.1

SUSE LE 12 SP4: new xen packages.
New packages are available:
  SUSE LE 12 SP4: xen 4.11.4_16-2.51.1

SUSE LE 15: new xen packages.
New packages are available:
  SUSE LE 15 RTM: xen 4.10.4_24-3.56.1
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