Citrix Hypervisor Security Update

Description of Problem

A security issue has been identified in Citrix Hypervisor that may allow privileged code running in a guest VM to infer details of some computations occurring in other VMs on the host. This may, for example, be used to infer a secret encryption key used by a web server in a different VM.

This issue has the following CVE identifier:

CVE ID

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Description

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Vulnerability Type

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Pre-conditions

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CVE-2020-28368

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Side-channel attack through exposed power-monitoring interface

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CWE-1300

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Malicious code executing on the host.

This issue affects all currently supported versions of Citrix Hypervisor up to and including Citrix Hypervisor 8.2 LTSR.

In addition, Citrix is aware of two recently disclosed issues affecting Intel CPUs which are addressed by updated microcode from Intel. Although these are issues in the underlying hardware platform, Citrix has included this updated microcode in the hotfixes associated with this bulletin to assist customers who have not obtained updated firmware from their hardware vendor. These issues have the following identifiers:

• CVE-2020-8696
• CVE-2020-8698

These CPU issues may allow code running in a VM to obtain data being used in computations within other VMs or other processes within the same VM.

Customers should note that it is necessary to reboot the host for the microcode update that protects against these Intel CPU issues to take effect. Customers who are using the Live Patching feature of Citrix Hypervisor and who do not need the microcode update (either because they are using a CPU from a different vendor or because they have already updated their host BIOS/UEFI firmware) do not need to reboot the host after applying the update.

What Customers Should Do

Citrix has released hotfixes to address this issue. Citrix recommends that affected customers install these hotfixes as their patching schedule allows. The hotfixes can be downloaded from the following locations:

Citrix Hypervisor 8.2 LTSR: CTX285172 – <https://support.citrix.com/article/CTX285172&gt;

Citrix Hypervisor 8.1: CTX285171 – <https://support.citrix.com/article/CTX285171&gt;

Citrix XenServer 7.1 LTSR CU2: CTX285170 – <https://support.citrix.com/article/CTX285170&gt;

Citrix XenServer 7.0: CTX285169 – <https://support.citrix.com/article/CTX285169&gt;

Customers who are using the Live Patching feature of Citrix Hypervisor should consider rebooting the host machine if they are in need of the microcode update described above.

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;_.

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;_.

Reporting Security Vulnerabilities

Citrix welcomes input regarding the security of its products and considers any and all potential vulnerabilities seriously. For details on our vulnerability response process and guidance on how to report security-related issues to Citrix, please visit the Citrix Trust Center at <https://www.citrix.com/about/trust-center/vulnerability-process.html&gt;.

Changelog

Date	Change
2020-11-12	Initial Publication
2020-11-26	CVE ID Added