ESB-2018.3314.2 - UPDATE [Virtual] Citrix XenServer: Denial of service - Existing account 2018-11-14

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             AUSCERT External Security Bulletin Redistribution

                              ESB-2018.3314.2
                     Citrix XenServer Security Update
                             14 November 2018

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        AusCERT Security Bulletin Summary
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Product:           Citrix XenServer
Publisher:         Citrix
Operating System:  Virtualisation
Impact/Access:     Denial of Service -- Existing Account
Resolution:        Patch/Upgrade
CVE Names:         CVE-2018-18883  

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

Revision History:  November 14 2018: Update with assigned CVE number 
                   October  29 2018: Initial Release

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CTX239100

Citrix XenServer Security Update

Security Bulletin
Priority: Medium
Created: 26 Oct 2018
Modified: 13 Nov 2018

Applicable Products

  * XenServer 7.6
  * XenServer 7.5
  * 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: 

  * Citrix XenServer 7.6
  * Citrix XenServer 7.5
  * Citrix XenServer 7.1 LTSR CU1 

The following vulnerabilities have been addressed: 

  * CVE-2018-18883: 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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Changelog

+-----------------------------------------------------------------------------+
|Date                                  |Change                                |
|--------------------------------------+--------------------------------------|
|26th October 2018                     |Initial Issue                         |
|--------------------------------------+--------------------------------------|
|1st November 2018                     |Update with assigned CVE number       |
+-----------------------------------------------------------------------------+

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