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             AUSCERT External Security Bulletin Redistribution

                Citrix XenServer Multiple Security Updates
                               22 March 2018


        AusCERT Security Bulletin Summary

Product:           Citrix XenServer
Publisher:         Citrix
Operating System:  Citrix XenServer
                   Linux variants
                   BSD variants
Impact/Access:     Execute Arbitrary Code/Commands -- Existing Account
                   Increased Privileges            -- Existing Account
                   Denial of Service               -- Existing Account
Resolution:        Patch/Upgrade
CVE Names:         CVE-2018-7541 CVE-2018-7540 CVE-2016-2074

Reference:         ESB-2018.0772

Original Bulletin: 

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Citrix XenServer Multiple Security Updates

Security Bulletin | Critical
| Created: 21 Mar 2018 | Modified: 21 Mar 2018

Applicable Products

  o XenServer 7.3
  o XenServer 7.2
  o XenServer 7.1 LTSR Cumulative Update 1
  o XenServer 7.0

Description of Problem

A number of vulnerabilities have been identified within Citrix XenServer that
could, if exploited, allow a malicious administrator of a guest VM to crash the
host and, for some XenServer versions, allow a remote attacker to compromise
the host.

The following vulnerabilities have been addressed:

  o CVE-2016-2074: openvswitch: MPLS buffer overflow vulnerability
  o CVE-2018-7540: DoS via non-preemptable L3/L4 pagetable freeing
  o CVE-2018-7541: grant table v2 -> v1 transition may crash Xen

The host compromise issue (CVE-2016-2074) affects Citrix XenServer versions 7.0
and 7.1 CU1 only.
The denial of service issues affect all supported versions of Citrix XenServer
prior to version 7.4.

Mitigating Factors

Customers using the "Linux bridge" networking mode are unaffected by the host
compromise issue.

What Customers Should Do

Hotfixes have been released to address these issues. Citrix strongly recommends
that affected customers install these hotfixes as soon as possible. The
hotfixes can be downloaded from the following locations:

Citrix XenServer 7.3: CTX233368 - https://support.citrix.com/article/CTX233368

Citrix XenServer 7.2: CTX233366 - https://support.citrix.com/article/CTX233366

Citrix XenServer 7.1 LTSR CU1: CTX233363 - https://support.citrix.com/article/
CTX233363 and CTX233365 - https://support.citrix.com/article/CTX233365

Citrix XenServer 7.0: CTX233362 - https://support.citrix.com/article/CTX233362 
and CTX233364 - https://support.citrix.com/article/CTX233364

These hotfixes are not livepatchable.

Citrix is actively working on remediating the denial of service issues for
releases that are End of Maintenance but not yet End of Life.

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/.

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. 

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


|Date                              |Change                                    |
|21st March 2018                   |Initial publication                       |

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