CVE-2016-7777 - Citrix XenServer Security Update

Description of Problem

A security vulnerability has been identified in Citrix XenServer that may allow malicious user code within an HVM guest VM to read or modify the contents of certain registers belonging to other tasks within that same guest VM.

This vulnerability affects all currently supported versions of Citrix XenServer up to and including Citrix XenServer 7.0.

The following vulnerability has been addressed:

• CVE-2016-7777 (Medium): CR0.TS and CR0.EM not always honored for x86 HVM guests

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Mitigating Factors

PV guest VMs are unaffected by this issue.

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What Customers Should Do

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 7.0: CTX217644– <https://support.citrix.com/article/CTX217644&gt;
• Citrix XenServer 6.5 SP1: CTX217643– <https://support.citrix.com/article/CTX217643&gt;
• Citrix XenServer 6.2 SP1: CTX217642– <https://support.citrix.com/article/CTX217642&gt;
• Citrix XenServer 6.0.2 Common Criteria: CTX217641– <https://support.citrix.com/article/CTX217641&gt;

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What Citrix Is Doing

Citrix is notifying customers and channel partners about this potential security issue. This article is also available from the Citrix Knowledge Center at _ <http://support.citrix.com/&gt;_.

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Obtaining Support on This Issue

If you require technical assistance with this issue, please contact Citrix Technical Support. Contact details for Citrix Technical Support are available at _ <https://www.citrix.com/support/open-a-support-case.html&gt;_.

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Reporting Security Vulnerabilities

Citrix welcomes input regarding the security of its products and considers any and all potential vulnerabilities seriously. For guidance on how to report security-related issues to Citrix, please see the following document: CTX081743 – Reporting Security Issues to Citrix

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