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AUSCERT External Security Bulletin Redistribution
ESB-2021.2369.3
Citrix Virtual Apps and Desktops Security Update
29 July 2021
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AusCERT Security Bulletin Summary
---------------------------------
Product: Citrix Virtual Apps and Desktops
Citrix XenApp / XenDesktop
Publisher: Citrix
Operating System: Windows
Virtualisation
Impact/Access: Increased Privileges -- Existing Account
Resolution: Patch/Upgrade
CVE Names: CVE-2021-22928
Original Bulletin:
https://support.citrix.com/article/CTX319750
Revision History: July 29 2021: Vendor added further mitigation advice and hofixes
July 19 2021: Vendor updated hotfixes for 1912 LTSR
July 14 2021: Initial Release
- --------------------------BEGIN INCLUDED TEXT--------------------
Citrix Virtual Apps and Desktops Security Update
Reference: CTX319750
Category : High
Created : 12 July 2021
Modified : 28 July 2021
Applicable Products
o Citrix Virtual Apps and Desktops
Description of Problem
A vulnerability has been identified in Citrix Virtual Apps and Desktops that
could, if exploited, allow a user of a Windows VDA that has either Citrix
Profile Management or Citrix Profile Management WMI Plugin installed to
escalate their privilege level on that Windows VDA to SYSTEM.
This vulnerability has the following identifier:
+--------------+--------------+-------------+---------------------------------+
|CVE ID |Description |Vulnerability|Pre-conditions |
| | |Type | |
+--------------+--------------+-------------+---------------------------------+
| |Local |CWE-284: |Authenticated access to a VDA |
|CVE-2021-22928|privilege |Improper |with Citrix Profile Management or|
| |escalation on |Access |Citrix Profile Management WMI |
| |a Windows VDA |Control |Plugin installed |
+--------------+--------------+-------------+---------------------------------+
The vulnerability affects the following supported versions of Citrix Virtual
Apps and Desktops and XenApp / XenDesktop:
o Citrix Virtual Apps and Desktops 2106 and earlier Current Release (CR)
versions
o Citrix Virtual Apps and Desktops 1912 LTSR CU3 and earlier versions of 1912
LTSR
o Citrix XenApp / XenDesktop 7.15 LTSR CU7 and earlier versions of 7.15 LTSR
Citrix Virtual Apps and Desktops 2106 is only affected when Citrix Profile
Management is installed on a Windows VDA as Citrix Profile Management WMI
Plugin is not affected in this version.
Please note that Citrix XenApp / XenDesktop 7.6 LTSR has now reached End of
Life and is no longer supported except through Citrix Extended Support Program.
Mitigating Factors
Customers are not affected by this issue if they have disabled Windows
Installer on Windows VDAs by configuring the Group Policy setting:
Computer Configuration\Administrative templates\Windows components\windows installer\Turn off Windows Installer
to Enabled - Always .
What Customers Should Do
Citrix has released hotfixes to address the vulnerability in the following
supported versions:
Citrix Virtual Apps and Desktops 2106
o Citrix Profile Management x86 - https://support.citrix.com/article/
CTX319995
o Citrix Profile Management x64 - https://support.citrix.com/article/
CTX319996
Citrix Virtual Apps and Desktops 1912 LTSR
o Citrix Profile Management x64 (3003) - https://support.citrix.com/article/
CTX322394
o Citrix Profile Management WMI Plugin x64 - https://support.citrix.com/
article/CTX319668
o Citrix Profile Management x86 (3003) - https://support.citrix.com/article/
CTX322395
o Citrix Profile Management WMI Plugin x86 - https://support.citrix.com/
article/CTX319671
Citrix XenApp / XenDesktop 7.15 LTSR
o Citrix Profile Management x64 - https://support.citrix.com/article/
CTX319817
o Citrix Profile Management WMI Plugin x64 - https://support.citrix.com/
article/CTX319669
o Citrix Profile Management x86 - https://support.citrix.com/article/
CTX319818
o Citrix Profile Management WMI Plugin x86 - https://support.citrix.com/
article/CTX319670
Customers who have installed both affected components should install all
applicable hotfixes. Customers who have only installed one of the affected
components should install the hotfix that applies to the component they have
installed.
Citrix recommends that customers install any applicable hotfixes on affected
Windows VDAs as soon as possible.
This issue will also be addressed in any future versions of Citrix Virtual Apps
and Desktops and Citrix XenApp / XenDesktop.
Acknowledgements
Citrix would like to thank Lasse Trolle Borup of Improsec A/S for working with
us to protect Citrix customers.
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 https://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/ .
Reporting Security Vulnerabilities to Citrix
Citrix welcomes input regarding the security of its products and considers any
and all potential vulnerabilities seriously. For details on our vulnerability
response process and guidance on how to report security-related issues to
Citrix, please see the following webpage: https://www.citrix.com/about/
trust-center/vulnerability-process.html .
Disclaimer
This document is provided on an "as is" basis and does not imply any kind of
guarantee or warranty, including the warranties of merchantability or fitness
for a particular use. Your use of the information on the document is at your
own risk. Citrix reserves the right to change or update this document at any
time.
Changelog
Date Change
2021-07-13 Initial Publication
2021-07-13 Additional hotfixes added
2021-07-16 Updated Profile Management hotfixes for 1912 LTSR (3002)
2021-07-23 Added mitigation advice and clarification for 7.6 LTSR
2021-07-28 Updated Profile Management hotfixes for 1912 LTSR (3003)
- --------------------------END INCLUDED TEXT--------------------
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