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CVE intelligence

CVE-2025-27466

Vulnerability intelligence

Published Sep 11, 2025Sources checked Oct 27, 2026
9.8CRITICALCVSS out of 10
What this means

Review the available evidence

CVE-2025-27466 and is rated Critical severity with a CVSS score of 9.8. It is not in the current CISA KEV record we collected. That does not prove exploitation has not occurred.

What to do next

Remediation and response

Citrix Security Bulletins guidance

Vendor revision: May 3, 2026
Vendor remediation details

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

CISA KEVNot listedBased on the latest collected catalog
EPSS0.5%Estimated 30-day exploitation probability
Ransomware useNot markedCISA KEV ransomware field
Threat actors0Source-linked actor relationships
Overview

What is CVE-2025-27466?

[This CNA information record relates to multiple CVEs; the text explains which aspects/vulnerabilities correspond to which CVE.]

There are multiple issues related to the handling and accessing of guest memory pages in the viridian code:

1. A NULL pointer dereference in the updating of the reference TSC area.

This is CVE-2025-27466.

2. A NULL pointer dereference by assuming the SIM page is mapped when a synthetic timer message has to be delivered.

This is CVE-2025-58142.

3. A race in the mapping of the reference TSC page, where a guest can get Xen to free a page while still present in the guest physical to machine (p2m) page tables.

This is CVE-2025-58143.

Source: NVD