Symptoms
After you install the April 11, 2023 updates for SharePoint Server 2016 (KB 5002385 and KB 5002370) on Windows Server 2012 R2, and then perform SharePoint upgrade actions through the SharePoint Products Configuration Wizard or the Upgrade-SPFarm PowerShell cmdlet, you may encounter the following issues:
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"HTTP Error 503. The service is unavailable" error occurs when browsing to SharePoint sites.
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Internet Information Services (IIS) application pools used by SharePoint fail to start. This impacts all SharePoint web applications, including the content web applications, the SharePoint Central Administration web application, and the SharePoint Web Services site.
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In the Application log of the Windows Event Log, event ID 2280 is recorded from the IIS-W3SVC-WP source with the following description:
The Module DLL <%CommonProgramFiles%>\Microsoft Shared\Web Server Extensions\16\isapi\sprequestfilteringmodule.dll failed to load. The data is the error.
Cause
The April 11, 2023 updates for SharePoint Server 2016 introduce Windows Antimalware Scan Interface (AMSI) integration to help protect SharePoint endpoints from potentially malicious web requests. AMSI integration is registered in IIS by an upgrade action that's performed when you run any of the following after installing the April 11, 2023 updates:
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SharePoint Products Configuration Wizard (PSConfigUI.exe)
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psconfig.exe -cmd upgrade -inplace b2b
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Upgrade-SPFarm
This issue occurs because AMSI integration isn't compatible with Windows Server 2012 R2. Therefore, when IIS tries to load the sprequestfilteringmodule DLL hosting the AMSI integration feature, it fails.
Resolution
To fix this issue, install the Description of the security update for SharePoint Enterprise Server 2016: June 13, 2023 (KB5002404).
