Hash: SHA256

             AUSCERT External Security Bulletin Redistribution

             Citrix Virtual Apps and Desktops Security Update
                             13 November 2020


        AusCERT Security Bulletin Summary

Product:           XenDesktop 7.6
                   XenDesktop 7.15
                   Citrix Virtual apps and desktop 7 1912 LTSR Cumulative Update 1
                   Citrix Virtual Apps and Desktops
Publisher:         Citrix
Operating System:  Citrix XenServer
Impact/Access:     Execute Arbitrary Code/Commands -- Existing Account
                   Increased Privileges            -- Existing Account
Resolution:        Patch/Upgrade
CVE Names:         CVE-2020-8270 CVE-2020-8269 

Original Bulletin: 

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

Citrix Virtual Apps and Desktops Security Update

Reference: CTX285059

Category : High

Created  : 10 Nov 2020

Modified : 10 Nov 2020

Applicable Products

  o XenDesktop 7.6
  o XenDesktop 7.15
  o Citrix Virtual apps and desktop 7 1912 LTSR Cumulative Update 1
  o Citrix Virtual Apps and Desktops

Description of Problem

Vulnerabilities have been identified in Citrix Virtual Apps and Desktops that
could, if exploited,result in:

  o A user who has access to a Windows Virtual Desktop being able to escalate their
    privilege level on that Windows Virtual Desktop to SYSTEM.
  o Remote compromise of a Windows Virtual Desktop which has Windows file sharing
    (SMB) enabled.

These vulnerabilities have the following identifiers:

|CVE ID       |Description               |Vulnerability Type|Pre-conditions         |
|             |An unprivileged Windows   |                  |The attacker must be   |
|             |user on the               |CWE-269: Improper |an authenticated       |
|CVE-2020-8269|VDA can perform arbitrary |Privilege         |user on the Windows    |
|             |command                   |Management        |VDA with write access  |
|             |execution as SYSTEM       |                  |to the C:\directory    |
|             |                          |CWE-78: Improper  |The attacker must be   |
|             |An unprivileged Windows   |Neutralization of |an authenticated       |
|             |user on the               |Special Elements  |user on the Windows    |
|CVE-2020-8270|VDA or a SMB user can     |used in an OS     |VDA or be authenticated|
|             |perform arbitrary command |Command ('OS      |to Windows SMB         |
|             |execution as SYSTEM       |Command           |service running        |
|             |                          |Injection')       |on the VDA             |

The vulnerabilities affect the following supported versions of Citrix Virtual Apps
and Desktops:

  o Citrix Virtual Apps and Desktops 2006 and earlier versions
  o Citrix Virtual Apps and Desktops 1912 LTSR CU1 and earlier versions of 1912
  o Citrix XenApp/XenDesktop7.15 LTSR CU6 and earlier versions of 7.15 LTSR
  o Citrix XenApp/XenDesktop7.6 LTSR CU8 and earlier versions of 7.6 LTSR

Please note that CitrixXenApp/XenDesktop 7.6 LTSR is not affected
by CVE-2020-8270.

Mitigating Factors

CVE-2020-8269- This issue is only exploitable if low-privilege users have been
granted permission to write files to the C:\ directory. This permission is not
default in Windows and Citrix recommends that users are only granted the
permissions they require.

CVE-2020-8270 - A remote compromise is only possible when Windows file sharing
(SMB) is enabled on the Windows Virtual Desktop. If authentication is required
for SMB then an attacker must also be able to authenticate in order to remotely
compromise the Virtual Desktop.

What Customers Should Do

The issues have been addressed in the following versions of Citrix Virtual Apps
and Desktops:

  o Citrix Virtual Apps and Desktops 2009 or later
  o Citrix Virtual Apps and Desktops 1912 LTSRCU1 hotfixes CTX285870,CTX285871,
    CTX285872 and CTX286120, and later cumulative updates
  o Citrix XenApp/XenDesktop7.15 LTSR CU6 hotfixes
    CTX285341,CTX285342 and CTX285344, and later cumulative updates
  o Citrix XenApp/XenDesktop7.6 LTSR CU9 and later cumulative updates

Citrix strongly recommends that customers upgrade to a fixed version as soon as

The latest versions of Citrix Virtual Apps and
Desktops are available from the following location:


Hot fixes to address the issues in Citrix Virtual Apps and Desktops 1912 LTSR
and Citrix XenApp/XenDesktop7.15 LTSR can be downloaded from the following locations:

Citrix Virtual Apps and Desktops1912 CU1

CTX285870 - https://support.citrix.com/article/CTX285870

CTX285871 - https://support.citrix.com/article/CTX285871

CTX285872 - https://support.citrix.com/article/CTX285872

CTX286120 - https://support.citrix.com/article/CTX286120

Citrix XenApp /XenDesktop7.15 CU6

CTX285341 - https://support.citrix.com/article/CTX285341

CTX285342 - https://support.citrix.com/article/CTX285342

CTX285344- https://support.citrix.com/article/CTX285344

Customers should ensure they have installed the latest cumulative update and
then apply all hotfixes for that version.


Citrix would like to thank HannayAl-Mohanna of F-Secure Consulting and Michael
Garrison of State Farm Information Security for working with us to protect Citrix


|Date                      |Change                                            |
|2020-11-10                |Initial Publication                               |

- --------------------------END INCLUDED TEXT--------------------

You have received this e-mail bulletin as a result of your organisation's
registration with AusCERT. The mailing list you are subscribed to is
maintained within your organisation, so if you do not wish to continue
receiving these bulletins you should contact your local IT manager. If
you do not know who that is, please send an email to auscert@auscert.org.au
and we will forward your request to the appropriate person.

NOTE: Third Party Rights
This security bulletin is provided as a service to AusCERT's members.  As
AusCERT did not write the document quoted above, AusCERT has had no control
over its content. The decision to follow or act on information or advice
contained in this security bulletin is the responsibility of each user or
organisation, and should be considered in accordance with your organisation's
site policies and procedures. AusCERT takes no responsibility for consequences
which may arise from following or acting on information or advice contained in
this security bulletin.

NOTE: This is only the original release of the security bulletin.  It may
not be updated when updates to the original are made.  If downloading at
a later date, it is recommended that the bulletin is retrieved directly
from the author's website to ensure that the information is still current.

Contact information for the authors of the original document is included
in the Security Bulletin above.  If you have any questions or need further
information, please contact them directly.

Previous advisories and external security bulletins can be retrieved from:


Australian Computer Emergency Response Team
The University of Queensland
Qld 4072

Internet Email: auscert@auscert.org.au
Facsimile:      (07) 3365 7031
Telephone:      (07) 3365 4417 (International: +61 7 3365 4417)
                AusCERT personnel answer during Queensland business hours
                which are GMT+10:00 (AEST).
                On call after hours for member emergencies only.
Comment: http://www.auscert.org.au/render.html?it=1967