Description of Problem
Several security issues have been discovered in Citrix Hypervisor that, collectively, may allow privileged code in a guest VM to compromise or crash the host.
These issues have the following identifiers:
All currently supported versions of Citrix Hypervisor are affected by all of these issues with the exception of CVE-2021-28699 which only affects Citrix Hypervisor 8.2 LTSR.
These issues have the following identifiers:
| CVE-ID | Description | Pre-requisites |
| CVE-2021-28694 | Host denial of service | Malicious privileged code execution in a guest VM running on a host with firmware that declares ACPI tables which includes memory regions that are identity mapped for devices that have been explicitly assigned, by the host administrator, to that guest VM in PCI passthrough mode. |
| CVE-2021-28697 | Host compromise | Malicious privileged code execution in a guest VM that has two or more vCPUs allocated to it |
| CVE-2021-28698 | Host denial of service | Malicious privileged code execution in a guest VM |
| CVE-2021-28699 | Host compromise | Malicious privileged code execution in a guest VM on a host where the host administrator has modified the guest or host grant table limits |
| CVE-2021-28701 | Host compromise | Malicious privileged code execution in a guest VM that has two or more vCPUs allocated to it |
All currently supported versions of Citrix Hypervisor are affected by all of these issues with the exception of CVE-2021-28699 which only affects Citrix Hypervisor 8.2 LTSR.
What Customers Should Do
Citrix has released hotfixes to address these issues. Citrix recommends that affected customers install these hotfixes as their patching schedule allows. The hotfixes can be downloaded from the following locations:
Citrix Hypervisor 8.2 LTSR: CTX324257 – https://support.citrix.com/article/CTX324257
Citrix Hypervisor 7.1 LTSR CU2: CTX324256 – https://support.citrix.com/article/CTX324256
Citrix Hypervisor 8.2 LTSR: CTX324257 – https://support.citrix.com/article/CTX324257
Citrix Hypervisor 7.1 LTSR CU2: CTX324256 – https://support.citrix.com/article/CTX324256
What Citrix is Doing
Citrix is 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/open-a-support-case.
Subscribe to Receive Alerts
Citrix strongly recommends that all customers subscribe to receive alerts when a Citrix security bulletin is created or modified at https://support.citrix.com/user/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.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. Citrix 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.