Description of Problem

Issues have been identified in the XenServer VM Tools for Windows that allow an attacker who has the ability to execute arbitrary unprivileged code within a guest Windows VM to compromise that same VM.  This issue affects Windows VMs running on either XenServer 8.4 and Citrix Hypervisor 8.2 CU1 LTSR.

These issues have the following identifiers:

• CVE-2025-27462

• CVE-2025-27463

• CVE-2025-27464

Affected Versions

The following supported versions of XenServer VM Tools for Windows are affected:

• All versions BEFORE 9.4.1

Linux guest VMs are not affected by this issue.

What Customers Should Do

We have released updated versions of the guest tools installer at https://support.citrix.com/s/article/CTX235403-updates-to-xenserver-vm-tools-for-windows-for-xenserver-and-citrix-hypervisor and we are also making them available through Windows Update. We recommend that customers ensure that these updates are applied to their guest Windows VMs using either one of these methods.  Alternatively, customers may use the guest Management Agent automatic update mechanism but customers should note that this will only be effective in addressing this issue if “Allow automatic I/O driver updates by the Management Agent” has been selected.

We particularly recommend that customers consider any MCS catalogs or PVS golden images that they may have deployed.

Note that remediation requires changes to Windows guest VMs.  Linux guest VMs are unaffected.  No changes are needed to the underlying XenServer/Citrix Hypervisor product.

What We Are Doing 

We are notifying customers and channel partners about this potential security issue through the publication of this security bulletin on the Citrix Knowledge Center at https://support.citrix.com/securitybulletins. 

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.

Subscribe to Receive Alerts

We strongly recommend that all customers subscribe to receive alerts when a security bulletin is created or modified at https://support.citrix.com/user/alerts.

Reporting Security Vulnerabilities to Us

We welcome input regarding the security of our products and consider any and all potential vulnerabilities seriously. For details on our vulnerability response process and guidance on how to report security-related issues to us, 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. Cloud Software Group reserves the right to change or update this document at any time. Customers are therefore recommended to always view the latest version of this document directly from the Citrix Knowledge Center.

Change log