Microsoft has fixed the Boot issue caused by the latest security update for Windows 10. This includes the latest KB4592438 update for Windows 10 versions 20H2 and 2004.

Because of this issue file system of Windows 10 devices get damaged resulting in Boot failure on running the Check Disk command chkdsk /f. Microsoft has informed that it can take up to 24 hours for the resolution to propagate to all devices.

Here is the detailed information provided by Microsoft about the fix.

This issue is resolved and should now be prevented automatically on non-managed devices. Please note that it can take up to 24 hours for the resolution to propagate to non-managed devices. Restarting your device might help the resolution apply to your device faster. For enterprise-managed devices that have installed this update and encountered this issue, it can be resolved by installing and configuring a special Group Policy. To find out more about using Group Policies, see Group Policy Overview.

To mitigate this issue on devices which have already encountered this issue and are unable to start up, use the following steps:

  1. The device should automatically start up into the Recovery Console after failing to start up a few times.
  2. Select Advanced options.
  3. Select Command Prompt from the list of actions.
  4. Once Command Prompt opens, type: chkdsk /f
  5. Allow chkdsk to complete the scan, this can take a little while. Once it has completed, type: exit
  6. The device should now start up as expected. If it restarts into Recovery Console, select Exit and continue to Windows 10.

Note After completing these steps, the device might automatically run chkdsk again on restart. It should start up as expected once it has completed.