The April Patch Tuesday update, which landed on April 9 for Windows systems, is still wreaking havoc on numerous systems. As we've previously reported, the KB4493472 has been especially problematic for antivirus programs -- Sophos Endpoint Protection was among the first to encounter problems, while Avira and Avast were other victims.
We're now learning that McAfee software has also been affected by the Patch Tuesday updates. In this case, two software programs have been identified by Microsoft and McAfee as currently being incompatible: McAfee Endpoint Security (ENS) Threat Prevention 10.x and McAfee Host Intrusion Prevention (Host IPS) 8.0.
According to Microsoft's updated release notes for KB4493472, systems with either of the above software packages installed may be incredibly slow to boot, or may become completely unresponsive after the system is restarted (following the installation of the update).
Microsoft says that it is currently working with McAfee engineers to resolve the issue, and an official patch will be issued once a solution has been identified. In the case of both software packages, affecting operating systems include Windows 7, Windows 8.1 and Windows 10 with the April 2019 update KBs installed.
McAfee advises that users disable Access Protection rules that protect a service as a workaround until a future update can be issued.
It should be noted that McAfee says that it has a proof of concept software fix has already been created, but customers will need to contact technical support by escalating a service request to obtain the software. You can create a service request by logging into the ServicePortal, or visit the following link for further guidance.
As for what is causing all of these problems with antivirus software in the first place, McAfee claims that the April Patch Tuesday updates introduced changes to the Client Server Runtime Subsystem (CSRSS) are creating the conflicts.