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 Citrix is 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/support-home/topic-article-list?trendingCategory=20&trendingTopicName=Security%20Bulletin 

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

Citrix strongly recommends that all customers subscribe to receive alerts when a security bulletin is created or modified at https://support.citrix.com/wolken-support/view/aboutsupport/my-support-alerts 

Reporting Security Vulnerabilities to Citrix

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 see the following webpage: https://www.cloud.com/trust-center/support 

Change Log

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Severity: Medium

Description of Problem

An issue has been identified in XenServer 8.4 which, when starting a VM on a host with limited available memory, may allow a privileged user in that newly starting VM to access memory data of a previously terminated VM. This issue has the following identifier:

• CVE-2026-4397

Affected Versions

This issue affects XenServer 8.4.

(Note that XenServer 9 is in Public Preview; releases in preview state are not intended for production use and so are not covered by security bulletins until they exit preview state.)