Citrix XenServer Multiple Security Updates

A number of security issues have been identified within Citrix XenServer. These issues could, if exploited, allow a malicious administrator of a PV guest VM to compromise the host. The issues have the identifiers:

• CVE-2017-8903 (High): x86: 64bit PV guest breakout via pagetable use-after-mode-change
• CVE-2017-8904 (High): grant transfer allows PV guest to elevate privileges
• CVE-2017-8905 (Low): possible memory corruption via failsafe callback

Customers using only HVM guest VMs are not affected. Note that all Microsoft Windows VMs are HVM.

To exploit these issues from a 32-bit PV guest VM, collaboration with the administrator of either an HVM guest VM or a 64-bit PV guest VM on the same host is required.  Customers using only 32-bit PV VMs are not affected.

Hotfixes have been released to address these issues. Citrix recommends that affected customers install these hotfixes, which can be downloaded from the following locations:

Citrix XenServer 7.1: CTX223290 – https://support.citrix.com/article/CTX223290

Citrix XenServer 7.0: CTX223289 – https://support.citrix.com/article/CTX223289 

Citrix XenServer 6.5 SP1: CTX223288 – https://support.citrix.com/article/CTX223288

Citrix XenServer 6.2 SP1: CTX223287 – https://support.citrix.com/article/CTX223287

Citrix XenServer 6.0.2 Common Criteria: CTX223286– https://support.citrix.com/article/CTX223286 

Customers who are using the Live Patching feature of Citrix XenServer 7.1 may apply the relevant hotfix without requiring a reboot.