Several security issues have been identified that affect Citrix Hypervisor:

Two issues, each of which may each allow privileged code in a guest VM to cause the host to crash or become unresponsive.  These two issues only affect systems where the malicious guest VM has a physical PCI device passed through to it by the host administrator.

These issues have the following identifiers:

• CVE-2021-27379
• CVE-2021-28692

A further issue that affects underlying CPU hardware.  Although this is not an issue in the Citrix Hypervisor product itself, Citrix is releasing hotfixes that also address this CPU issue.  This issue is of a type known as “speculative execution attacks” and may allow malicious code running on a CPU to infer the value of registers or memory belonging to other processes running on that CPU.

This issue has the following identifiers:

• CVE-2021-0089 (Intel CPUs)/CVE-2021-26313 (AMD CPUs)

 

CVE ID	Description	Pre-conditions
CVE-2021-27379	privileged code in a guest VM may cause the host to crash or become unresponsive	malicious guest VM must have a physical PCI device passed through by the host administrator and the attacker must be able to execute privileged code
CVE-2021-28692	privileged code in a guest VM may cause the host to crash or become unresponsive	malicious guest VM must have a physical PCI device passed through by the host administrator and the attacker must be able to execute privileged code
CVE-2021-0089/CVE-2021-26313	malicious code running on a CPU could infer the value of registers or memory belonging to other processes running on that CPU	Ability to execute code in a guest VM

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Mitigating Factors

Customers who have not assigned a PCI device to a guest VM are not affected by CVE-2021-27379 or CVE-2021-28692

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Instructions

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: CTX313807 – https://support.citrix.com/article/CTX313807
Citrix XenServer 7.1 LTSR CU2: CTX313806 – https://support.citrix.com/article/CTX313806
 

Date	Change
2021-06-09	Initial Publication