After September 2025 CU for SharePoint Server Subscription Edition application pool worker process might crash with Exception code 0xC0000409. Event log will contain entries similar to this:
Faulting application name: w3wp.exe, version: 10.0.17763.1, time stamp: 0xcfdb13d8
Faulting module name: owssvr.dll, version: 16.0.19127.20100, time stamp: 0x689cd397
Exception code: 0xc0000409
Fault offset: 0x000000000033b39b
Faulting process id: 0x32fc
Faulting application start time: 0x01dc37c6ba77ea7f
Faulting application path: c:\windows\system32\inetsrv\w3wp.exe
Faulting module path: C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\16\isapi\owssvr.dll
Report Id: 5b82605c-4db9-42ec-b10c-6462e8073a24
Faulting module name: owssvr.dll, version: 16.0.19127.20100, time stamp: 0x689cd397
Exception code: 0xc0000409
Fault offset: 0x000000000033b39b
Faulting process id: 0x32fc
Faulting application start time: 0x01dc37c6ba77ea7f
Faulting application path: c:\windows\system32\inetsrv\w3wp.exe
Faulting module path: C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\16\isapi\owssvr.dll
Report Id: 5b82605c-4db9-42ec-b10c-6462e8073a24
Reference:
Solution:
February 2026 CU for SharePoint Server Subscription Edition includes a fix for this issue:
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Hi Stefan,
By the way, this CU helped us with a crazy error.
If you want to use Sharegate to copy a site from an SE farm to a tenant, the copy process paralyzes the entire farm. Access to sites is no longer possible. If you cancel the copy process, everything runs normally again.
Now everything is working again and we can start the week happily 🙂
Best regards,
Marcel