Windows 10 critical process failure: Microsoft admits June updates are triggering reboots

Forced reboots are affecting some machines running Windows 10 version 1809 and above.

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Microsoft has admitted that this month's Windows 10 Patch Tuesday updates are causing more problems, this time resulting in crashes due to a failure in the Local Security Authority Subsystem Service (LSASS) file, lsass.exe.

It confirmed the new bug in the KB articles for updates to Windows 10 version 1809 (KB4561608), version 1903 and version 1909 (KB4560960), and version 2004 (KB4557957). 

Microsoft also notes that the June 16 out-of-band update – which fixed printers that stopped working after installing the Patch Tuesday updates – is affected by the LSASS failure.

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"The Local Security Authority Subsystem Service (LSASS) file (lsass.exe) might fail on some devices with the error message, 'A critical system process, C:\WINDOWS\system32\lsass.exe, failed with status code c0000008. The machine must now be restarted'," Microsoft explains. 

Microsoft says it is working on a fix that will be delivered in a future update. It has not confirmed whether the LSASS issue affects earlier versions of Windows 10. 

While the June updates appear to be the cause of the LSASS reboots, Bleeping Computer points to a user report from late May about machines running Windows 10 version 1809 seeing the error code described in Microsoft's known issues. 

"Event Viewer Log shows that LSASS.exe crashed on the first boot with error c0000008 and then all services failed to authenticate after, which probably caused the crash," the user wrote

It's not known when the update will arrive, but Microsoft is restarting its optional non-security update releases – the C and D week releases – in July, after pausing them in March to reduce the load on IT admins during the coronavirus outbreak. 

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The optional releases will only be available for Windows 10 and Windows Server, version 1809 and later. These give admins a chance to test non-security fixes coming in the following month's Patch Tuesday update, or B release. 

Microsoft is now calling the C and D releases Preview releases, which will be delivered in the third week – aka the C week – of each month. IT pros using Windows Server Update Services (WSUS) to manage updates will no longer see Preview or C releases for Windows 10 or Windows Server in the WSUS channel.