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01 November 2019

Protect yourself against future threats.

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             AUSCERT External Security Bulletin Redistribution

                        Hypervisor Security Update
                              1 November 2019


        AusCERT Security Bulletin Summary

Product:           Citrix Hypervisor
Publisher:         Citrix
Operating System:  Citrix XenServer
Impact/Access:     Increased Privileges -- Existing Account
                   Denial of Service    -- Existing Account
Resolution:        Patch/Upgrade
CVE Names:         CVE-2019-18425 CVE-2019-18424 CVE-2019-18421

Original Bulletin: 

- --------------------------BEGIN INCLUDED TEXT--------------------

Hypervisor Security Update

Reference: CTX263477

Category : High

Created  : 31 Oct 2019

Modified : 31 Oct 2019

Applicable Products

  o Citrix Hypervisor 8.0
  o XenServer 7.6
  o XenServer 7.1 LTSR Cumulative Update 2
  o XenServer 7.0

Description of Problem

A number of vulnerabilities have been found in Citrix Hypervisor (formerly
Citrix XenServer) that allow the host to be compromised by:

i. Privileged code in a guest VM that has been assigned a PCI passthrough

ii. Privileged code in a PV guest VM

iii. Unprivileged code in a 32-bit PV guest VM

These vulnerabilities have the following identifiers:

o CVE-2019-18420

o CVE-2019-18421

o CVE-2019-18424

o CVE-2019-18425

These issues affect all currently supported versions of Citrix Hypervisor up to
and including Citrix Hypervisor 8.0.

Mitigating Factors

Customers running only HVM workloads and not making use of PCI passthrough
functionality are not affected by these issues. Note that all Microsoft Windows
VMs run as HVM VMs.

What Customers Should Do

Hotfixes have been released to address these issues. Citrix recommends that
affected customers install these hotfixes as their patching schedules allow.
The hotfixes can be downloaded from the following locations:

Citrix Hypervisor 8.0:

CTX262555 - https://support.citrix.com/article/CTX262555

CTX258428 - https://support.citrix.com/article/CTX258428

Citrix XenServer 7.6:

CTX262554 - https://support.citrix.com/article/CTX262554

CTX258425 - https://support.citrix.com/article/CTX258425

Citrix XenServer 7.1 LTSR CU2:

CTX262553 - https://support.citrix.com/article/CTX262553

CTX258424 - https://support.citrix.com/article/CTX258424

Citrix XenServer 7.0:

CTX258417 - https://support.citrix.com/article/CTX258417

CTX258423 - https://support.citrix.com/article/CTX258423


|Date                                |Change                                  |
|31st October 2019                   |Initial publication                     |

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