Microsoft and McAfee have identified an issue with McAfee antivirus software that is causing Windows to boot slower or freeze. The problem is caused by changes in the Windows Client Server Runtime Subsystem service, otherwise known as CRSS, which introduced a deadlock with their software. Windows 10 may also be affected by the problem, according to McAfee support articles from the support articles for the Windows 8.1 and the Windows 7.1 updates. Avast’s support article contains a fix related to CRSS.
Source: https://www.bleepingcomputer.com/news/microsoft/windows-april-updates-also-have-problems-with-mcafee-software/