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. However, customers should note that the AMD microcode update provided is only effective on systems where the system firmware ("BIOS") has been updated to a version that includes a fix for CVE-2024-36347. This may be marked in the firmware release notes by reference to the firmware containing “AGESA PI 1.0.0.4” or later. Customers who are uncertain about their firmware version are recommended to contact their hardware vendor.  

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.

Change Log

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: Medium

Description of Problem

A hardware issue has been identified in AMD Zen 5 CPU devices that may cause those CPUs to return a value of zero more frequently than statistically expected when asked to generate a random value. This may compromise e.g. cryptographic keys that are generated by software that relies on the randomness of these values. Although this is not a vulnerability in the XenServer product itself, for the convenience of customers we are providing an update that contains updated AMD microcode to mitigate this CPU hardware issue. However, customers are advised to note the further actions described below.

This issue only affects certain AMD CPUs; customers who are running Intel-based systems are not affected by this issue.

This issue has the following identifier:

• CVE-2025-62626

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.)