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                             CERT-Renater

                 Note d'Information No. 2018/VULN341
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DATE                : 29/10/2018

HARDWARE PLATFORM(S): /

OPERATING SYSTEM(S):Systems running Citrix XenServer versions 7.6, 7.5,
                                   7.1 LTSR CU1.

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https://support.citrix.com/article/CTX239100
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CTX239100

Citrix XenServer Security Update

Security Bulletin

Severity: Medium
Created: 26 Oct 2018
Modified: 26 Oct 2018

Applicable Products

  o XenServer 7.6
  o XenServer 7.5
  o XenServer 7.1 LTSR Cumulative Update 1

Description of Problem

A security issue has been identified in Citrix XenServer that may
allow a malicious administrator of an HVM guest VM to crash the host.

This issue affects the following versions of Citrix XenServer:

  o Citrix XenServer 7.6
  o Citrix XenServer 7.5
  o Citrix XenServer 7.1 LTSR CU1

The following vulnerabilities have been addressed:

  o CVE-2018-TBA: Nested VT-x usable even when disabled

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Mitigating Factors

Customers with only PV guests are not affected by this issue.

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What Customers Should Do

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


Citrix XenServer 7.6: CTX239128 -
https://support.citrix.com/article/CTX239128
Citrix XenServer 7.5: CTX239127 -
https://support.citrix.com/article/CTX239127
Citrix XenServer 7.1 LTSR CU1: CTX239126 -
https://support.citrix.com/article/
CTX239126

Customers who are using the LivePatching feature of Citrix XenServer
will not need to reboot servers to apply this hotfix if those servers
were previously fully patched.

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Acknowledgements

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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/.

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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.

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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
     |
+--------------------------------------+--------------------------------------+
|26th October 2018                     |Initial Issue
     |
+--------------------------------------+--------------------------------------+

=========================================================
+ CERT-RENATER        | tel : 01-53-94-20-44            +
+ 23/25 Rue Daviel    | fax : 01-53-94-20-41            +
+ 75013 Paris         | email:cert@support.renater.fr   +
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