A vulnerability has been identified in the automatic update service of Citrix Workspace app for Windows that could result in:

• A local user escalating their privilege level to that of an administrator on the computer running Citrix Workspace app for Windows.

• A remote compromise of the computer running Citrix Workspace app when Windows file sharing (SMB) is enabled.

The issue has the following identifier: 

• CVE-2020-8207

This vulnerability affects the following supported versions of Citrix Workspace app for Windows:

• Citrix Workspace app 2002, 2006 and 2006.1 for Windows
• Citrix Workspace app 1912 LTSR for Windows (before CU1 Hotfix 1)

Note that this vulnerability was originally reported against a subset of the versions above. However, further investigation has discovered potential variant forms of this attack and the affected versions have been amended accordingly.

This vulnerability does not affect Citrix Workspace app on any other platforms or any supported versions of Citrix Receiver.

This vulnerability only exists if Citrix Workspace app was installed using an account with local or domain administrator privileges.  It does not exist when a standard Windows user installed Citrix Workspace app for Windows.

A remote compromise is only possible when the user has enabled Windows file sharing (SMB) and only when the updater service is running.  If authentication is required for SMB then an attacker must be able to authenticate before they could exploit this issue.

Users with automatic updates enabled and applied should have already been updated to a fixed version.

The issue has been addressed in the following versions of Citrix Workspace app for Windows: 

• Citrix Workspace App 2008 or later
• Citrix Workspace App 1912 LTSR CU1 Hotfix 1 (19.12.1001) and later cumulative updates

Note that these versions have been updated since the original publication of this bulletin.

Citrix strongly recommends that customers check if the version they are running has been automatically updated and, if necessary, upgrade to a fixed version as soon as possible.

The latest version of Citrix Workspace app for Windows is available from the following Citrix website location:

https://www.citrix.com/downloads/workspace-app/windows/

The latest LTSR version of Citrix Workspace app for Windows is available from the following Citrix website location:

https://www.citrix.com/downloads/workspace-app/workspace-app-for-windows-long-term-service-release/

Citrix would like to thank Ceri Coburn at Pen Test Partners for working with us to protect Citrix customers during both the initial disclosure of this issue and subsequent variants.

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 visit the Citrix Trust Center at https://www.citrix.com/about/trust-center/vulnerability-process.html.