Citrix XenServer Security Update

A number of security vulnerabilities have been identified in Citrix XenServer that have deployment-dependent impacts.

These issues affect the following supported versions of Citrix XenServer:

• Citrix XenServer 7.6
• Citrix XenServer 7.5
• Citrix XenServer 7.1 LTSR CU1
• Citrix XenServer 7.0

The following issues have been addressed:

• CVE-2018-19961 / CVE-2018-19962: insufficient TLB flushing/improper large page mappings with AMD IOMMUs

This issue may allow code in an HVM guest VM to compromise the host.

This issue is limited to guests that are using the PCI passthrough feature in conjunction with AMD CPUs.

• CVE-2018-19965: x86: DoS from attempting to use INVPCID with a non-canonical address

This issue may allow privileged code in a PV guest VM to crash the host.

This issue is limited to hosts with Intel CPUs that support the INVPCID instruction.

This issue only occurs in Citrix XenServer 7.6.

• CVE-2018-19967: Intel Erratum: “Processor May Hang When Executing Code In an HLE Transaction”.

This issue may allow code running in a guest VM to cause the host to become unresponsive and/or crash.

This issue is limited to hosts with Intel CPUs that are affected by the corresponding Intel erratum.

Hotfixes have been released to address these issues. Citrix recommends that affected customers install these hotfixes as their patching schedule permits. The hotfixes can be downloaded from the following locations:

Citrix XenServer 7.6: CTX239437 – https://support.citrix.com/article/CTX239437 

Citrix XenServer 7.5: CTX239436 – https://support.citrix.com/article/CTX239436 

Citrix XenServer 7.1 LTSR CU1: CTX239435 – https://support.citrix.com/article/CTX239435 

Citrix XenServer 7.0: CTX239434 – https://support.citrix.com/article/CTX239434