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             AUSCERT External Security Bulletin Redistribution

                     Citrix XenServer Security Update
                              9 January 2019


        AusCERT Security Bulletin Summary

Product:           Citrix XenServer
Publisher:         Citrix
Operating System:  Citrix XenServer
Impact/Access:     Root Compromise   -- Existing Account
                   Denial of Service -- Existing Account
Resolution:        Patch/Upgrade
CVE Names:         CVE-2018-19967 CVE-2018-19965 CVE-2018-19962

Reference:         ESB-2019.0060

Original Bulletin: 

Revision History:  January   9 2019: Updated CVE identifiers for TBA entries
                   November 21 2018: Initial Release

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Citrix XenServer Security Update

Created: 20 Nov 2018 | Modified: 08 Jan 2019

Applicable Products

  o XenServer 7.6
  o XenServer 7.5
  o XenServer 7.1 LTSR Cumulative Update 1
  o XenServer 7.0

Description of Problem

A number of security vulnerabilities have been identified in Citrix XenServer
that have deployment-dependent impacts.

These issues affect the following supported versions of Citrix XenServer:

  o Citrix XenServer 7.6
  o Citrix XenServer 7.5
  o Citrix XenServer 7.1 LTSR CU1
  o Citrix XenServer 7.0

The following issues have been addressed:

  o CVE-2018-19961 / CVE-2018-19962: insufficient TLB flushing/improper large
    page mappings with AMD IOMMUs

This issue may allow code in an HVM guest VM to compromise the host.

This issue is limited to guests that are using the PCI passthrough feature in
conjunction with AMD CPUs.

  o CVE-2018-19965: x86: DoS from attempting to use INVPCID with a
    non-canonical address

This issue may allow privileged code in a PV guest VM to crash the host.

This issue is limited to hosts with Intel CPUs that support the INVPCID

This issue only occurs in Citrix XenServer 7.6.

  o CVE-2018-19967: Intel Erratum: "Processor May Hang When Executing Code In
    an HLE Transaction".

This issue may allow code running in a guest VM to cause the host to become
unresponsive and/or crash.

This issue is limited to hosts with Intel CPUs that are affected by the
corresponding Intel erratum.


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What Customers Should Do

Hotfixes have been released to address these issues. 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: CTX239437 - https://support.citrix.com/article/CTX239437 

Citrix XenServer 7.5: CTX239436 - https://support.citrix.com/article/CTX239436 

Citrix XenServer 7.1 LTSR CU1: CTX239435 - https://support.citrix.com/article/

Citrix XenServer 7.0: CTX239434 - https://support.citrix.com/article/CTX239434 


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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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|Date                    |Change                                              |
|20th November 2018      |Initial Issue                                       |
|8th January 2019        |Updated CVE identifiers for TBA entries             |

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