Virtual Delivery Agent for Windows used by Citrix Virtual Apps and Desktops and Citrix DaaS contains the vulnerability mentioned below:

What Customers Should Do

Citrix strongly recommends that customers upgrade their Windows Virtual Delivery Agent for single-session OS to versions that contain the fixes as soon as possible.  

Windows Virtual Delivery Agent versions that contain the fixes are: 

Current Release (CR)

• Citrix Virtual Apps and Desktops 2503 and later versions 

The following Updates have been released to address the issues in Citrix Virtual Apps and Desktops 2402 LTSR CU1 and CU2.  Customers should ensure they have installed the corresponding cumulative update and then install any applicable updates: 

Long Term Service Release (LTSR)

• Citrix Virtual Apps and Desktops 2402 LTSR CU1 Update 1 - https://support.citrix.com/support-home/kbsearch/article?articleNumber=CTX694848
• Citrix Virtual Apps and Desktops 2402 LTSR CU2 Update 1 - https://support.citrix.com/support-home/kbsearch/article?articleNumber=CTX694849  
  and later cumulative 

Additional Information:

Citrix Virtual Apps and Desktops and Citrix DaaS customers may use Citrix provisioning services or Machine creation services technologies, if applicable, to update their non-persistent Virtual Delivery Agents to the Current Release (CR) Citrix Virtual Apps and Desktops 2503 or later.

Citrix DaaS customers may use VDA Upgrade Service (VUS) to update their Windows persistent Virtual Delivery Agents for Remote PC Access, HDX Plus for Windows 365, and any other persistent or provisioned and dedicated catalogs. Customers are recommended to review the VUS Prerequisites to determine if they can use the VDA Upgrade Service.

Workarounds/ Mitigating Factors

While applying the recommended hotfixes is the preferred solution, customers who are unable to upgrade immediately can apply the following registry change as a temporary workaround  on affected systems:

[HKEY_LOCAL_MACHINE\SOFTWARE\Citrix\CtxExceptionHandler]

"Enabled"=dword:00000000

A system restart is required after editing the registry for the changes to take effect. For any non-persistent VDAs, integrate all registry modifications into the master image.

Note: Customers may leverage Citrix Workspace Environment Management to deploy the above registry key. More details can be found here: https://docs.citrix.com/en-us/workspace-environment-management/current-release/user-interface-description/actions/group-policy-settings.html

Acknowledgments

Cloud Software Group thanks Timm Lippert and Christopher Beckmann from SySS GmbH, as well as Brandon Fisher, Security Consultant from Rapid7, for working with us in protecting Cloud Software Group customers.

The information on this page is being provided to you on an "AS IS" and "AS-AVAILABLE" basis. The issues described on this page may or may not impact your system(s). Cloud Software Group, Inc. and its subsidiaries (collectively, "Cloud SG") make no representations, warranties, or guarantees as to the information contained herein. ANY AND ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING, WITHOUT LIMITATION, INCLUDING, BUT NOT LIMITED TO, IMPLIED WARRANTIES OF MERCHANTABILITY, NON-INFRINGEMENT AND FITNESS FOR A PARTICULAR PURPOSE ARE HEREBY DISCLAIMED. BY ACCESSING THIS PAGE, YOU ACKNOWLEDGE THAT CLOUD SG SHALL IN NO EVENT BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, PUNITIVE, OR CONSEQUENTIAL DAMAGES THAT ARISE OUT OF YOUR USE OR FAILURE TO USE THE INFORMATION CONTAINED HEREIN. Cloud SG reserves the right to change or update the information on this page at any time. We accordingly recommend that you always view the latest version of this page. The information contained herein is being provided to you under the terms of your applicable customer agreement with Cloud SG, and may be used only for the purposes contemplated by such agreement. If you do not have such an agreement with Cloud SG, this information is provided under the cloud.com Terms of Use, and may be used only for the purposes contemplated by such Terms of Use.

Severity - High

Description of Problem

A vulnerability has been identified that impacts Virtual Delivery Agent for Windows used by Citrix Virtual Apps and Desktops and Citrix DaaS. 

Affected Versions: 

The vulnerability affects the following supported versions of Windows Virtual Delivery Agent for single-session OS: 

Current Release (CR)

• Citrix Virtual Apps and Desktops versions before 2503 

Long Term Service Release (LTSR)

• Citrix Virtual Apps and Desktops 2402 LTSR CU2 and earlier versions of 2402 LTSR

Note: Citrix Virtual Apps and Desktops 2203 LTSR is not affected by this vulnerability.