Two security issues have been identified in Citrix Hypervisor (formerly Citrix XenServer) that may allow privileged code in a guest VM to cause the host to crash or become unresponsive.
These issues affect all currently supported versions of Citrix Hypervisor up to and including Citrix Hypervisor 8.2 LTSR.
An additional issue has been identified in Citrix Hypervisor 8.2 LTSR (only) that may allow malicious network traffic to cause subsequent packets to be dropped.
CVE-2021-28038 – An attacker with the ability to execute privileged mode code in a guest can perform a denial of service attack against the host
CVE-2021-28688 – An attacker with the ability to execute privileged mode code in a guest can perform a denial of service attack against the host.
CVE-2020-35498 – Malicious network traffic on the local network may cause subsequent packets to be dropped.
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 XenServer 7.1 LTSR CU2: CTX306480 – https://support.citrix.com/article/CTX306480
Citrix XenServer 7.0: CTX306482 – https://support.citrix.com/article/CTX306482