Microsoft recently released the Patch Tuesday update KB4549951 (Builds 18363.778 and 18362.778) for Windows 10 version 1903/1909. It followed up KB4549951 with optional update KB4550945 (Builds 18363.815 and 18362.815 for version 1909/1903).

While we had reported about some users facing various issues after installing KB4549951 it seems that there are even more serious issues caused by the update including BSOD, Boot failures, WiFi connectivity issues, and more.

Users have reported about facing dreaded BSOD after implementing the update KB4549951.

Help to diagnose Kernel Mode Heap Corruption

Split from my posts from the Cumulative updates – April 14 2020 thread.

Lately, I’ve been getting BSODs with the error “KERNEL MODE HEAP CORRUPTION” whenever I try to do something seemingly CPU-heavy (watching livestreams/conferences, even trying to look at the Event Viewer). Following some experimenting, I noted that the KB4549951 update was not necessarily the cause of the BSOD because it happened even after I uninstalled it. I have recently updated my Intel display driver, but I can’t seem to roll it back from the Device Manager.


I have been getting BSOD after watching streams on twitch and even while watching youtube videos sometimes and it happend while I tried to install windows update (KB4549951). This is a PC I bought new 4 months ago.  I have been searching for an answer but couldn’t find something useful so I decided to ask you guys.

Boot failures 1 and WiFi connectivity issues are also being reported.

After attempting to install what I believe to be KB4549951, my laptop will no longer boot. The update proceeded normally when shutting down the PC, but when turning it on, the boot screen quickly says “Preparing Automatic Repair”, which then becomes “Diagnosing your PC”, then “Attempting repairs”. I am then brought to the Automatic Repair screen the tells me it couldn’t repair my PC and points me to a log file. I have have tried:

  • Startup Repair, which simply repeats the process
  • Startup Settings, which also repeats the process
  • System Restore, which fails after ~5 minutes
  • Uninstall latest quality update, which tells me I have pending update actions and to use Startup Repair
  • Uninstall latest feature update, which fails and tells me to reset the PC
  • Resetting the PC, which fails
  • Using a drive with the Windows 10 Installation media to run Startup Repair through the “Repair this computer” option.

Is there anything else I can do to get my computer to boot short of formatting the drive and reinstalling Windows?

No more wifi since last windows update

Since the KB4549951 I have no more wifi on my computer.

I already tried all those, unsuccesfully:
– Uninstall update

– All the problem resolution software inside windows

– Restart the services linked to network

– Updating the drivers (drivers are up to date for sure now)

– Adding a usb wifi adapter, doesn’t work either

Even the optional update KB4550945 is failing to install, making speakers not work and causing Defender Firewall to block Microsoft services.

April 21, 2020—KB4550945 (OS Builds 18362.815 and 18363.815): Installed this update and my speakers do not work
Hi. I did the above-mentioned update and my speakers do not work thereafter. Sound is playing but I don’t hear anything. When I plug my headset into my laptop, sound can be heard but the usual dialogue box that opens when I plug in, does not appear. How do I rectify this? Please help.

Update fail
2020-04 Cumulative Update for Windows 10 Version 1909 for x64-based Systems (KB4550945) – Error 0x800f0986

Windows Defender Firewall is blocking Microsoft services

I noticed that after the latest optional software update for Windows 10, the Windows Defender firewall is blocking Microsoft services: KB4550945

In my case, it is not allowing downloading or logging in on the App Store.

It even blocks logging in to via browser.

Turning off Firewall allows me to log in normally and perform app updates via App Store.

Can this be checked please?

Is there any additional information needed?