CVE-2018-3639 - Citrix XenServer Security Update

Description of Problem

CVE-2018-3639 Speculative Store Bypass Disable is an issue that may affect third-party software that runs in guest VMs on Citrix XenServer. This is not an issue caused by Citrix XenServer and Citrix is unaware of any means of exploiting this issue against XenServer itself.
Third-party software can mitigate this issue by restructuring of the code; for Intel CPUs, third-party software may instead choose to mitigate this issue by selectively enabling and disabling a CPU feature known as memory disambiguation. This requires both new host firmware and the new functionality of that firmware to be exposed to guest VMs. To expose this firmware functionality, Citrix is releasing hotfixes for supported versions of Citrix XenServer 7.x.

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What Customers Should Do

Customers wishing to expose the new host firmware functionality to their guest VMs should install both the Citrix XenServer hotfixes and updated host firmware or BIOS code. The locations of the Citrix XenServer hotfixes are listed below; Citrix recommends following your hardware supplier’s guidance for firmware updates.

Citrix XenServer 7.4: CTX235133 – <https://support.citrix.com/article/CTX235133&gt;

Citrix XenServer 7.3: CTX235132 – <https://support.citrix.com/article/CTX235132&gt;

Citrix XenServer 7.1 LTSR CU1: CTX235131 – <https://support.citrix.com/article/CTX235131&gt;

Citrix XenServer 7.0: CTX235130 – <https://support.citrix.com/article/CTX235130&gt;

Note that, in line with previous issues that were not vulnerabilities in Citrix XenServer, mitigations are not available for versions 6.x of Citrix XenServer.

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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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Changelog

Date	Change
22nd May 2018	Initial Publication

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