Users of McAfee anti-virus are reporting serious issues after installing April security updates for Windows 7 and 8.1. The updates previously caused issues with variants of Avast, AVG, Arcabit, and Sophos.

According to Microsoft, users with McAfee may experience significant slowdown or unresponsiveness when booting or restarting their PC. The issue appears to be with changes to Windows’ Client Server Runtime Subsystem, which McAfee says “introduced a potential deadlock” with its Endpoint Security.

McAfee has released a proof-of-concept fix while it investigates. The issue is present on McAfee Security ENS 10.x, Host IPS 8.0, and VirusScanEnterprise 8.8. Though Microsoft blocked the update for users of Sophos, Avira, and ArcaBit, it’s yet to announce similar measures for McAfee.

April Security Update Patch Notes

The April 9 monthly rollup includes fixes from KB4489892, some of which are very important for security. These include protections against the Spectre Variant 2 and Meltdown CPU flaws for VIA-based computers.

The update also fixes the following:

  • “Addresses an issue that causes the error “0x3B_c0000005_win32k!vSetPointer” when the kernel mode driver, win32k.sys, accesses an invalid memory location.
  • Addresses an issue in which netdom.exe fails to run, and the error, “The command failed to complete successfully” appears.
  • Addresses an issue that may prevent Custom URI Schemes for Application Protocol handlers from starting the corresponding application for local intranet and trusted sites on Internet Explorer.
  • Addresses an issue that may cause authentication issues for Internet Explorer 11 and other applications that use WININET.DLL. This occurs when two or more people use the same user account for multiple, concurrent login sessions on the same Windows Server machine, including Remote Desktop Protocol (RDP) and Terminal Server logons.
  • Addresses an issue that may cause compound document (OLE) server applications to display embedded objects incorrectly if you use the PatBlt API to place embedded objects into the Windows Metafile (WMF).
  • Security updates to Windows Kernel, Windows Server, Graphics Component, Windows Input and Composition, Windows Datacenter Networking, Windows MSXML, and the Microsoft JET Database Engine”.