What Customers Should Do

We have pushed updates to both the Early Access and Normal update channels of XenServer 8.4. We recommend that customers update to the latest version from their chosen channel following the instructions at https://docs.xenserver.com/en-us/xenserver/8/update 

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

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.

Severity: High

Description of Problem

Several issues have been identified in XenServer 8.4 that collectively may allow privileged code in a guest VM to compromise or crash the host. 

These issues have the following identifiers:

• CVE-2025-27466
• CVE-2025-58142
• CVE-2025-58143
• CVE-2025-58146

Affected Versions

These issues affect XenServer 8.4.

(Note that Citrix Hypervisor 8.2 CU1 is now End of Life (EoL) and so no longer receives security updates or security bulletins.)