ArcGIS Web Adaptor (IIS) Stability Patch

Esri announces the ArcGIS Web Adaptor (IIS) Stability Patch. This patch addresses an issue when a burst of concurrent requests through the ArcGIS Web Adaptor (IIS) may result in GIS Server instability if HTTP/2 is enabled on Microsoft IIS. Esri recommends all users of the ArcGIS Web Adaptor (IIS) for ArcGIS Enterprise versions 11.3 and 11.5 apply this patch. This patch deals specifically with the issues listed below under Issues Addressed with this Patch.

Applying the ArcGIS Web Adaptor (IIS) Stability Patch will update all ArcGIS Web Adaptors (IIS) on a machine. Regarding the typical patch finding and notification tools, you will experience some limitations for this ArcGIS Web Adaptor (IIS) Stability Patch. The PatchFinder.exe will show multiple web adaptors as of version 11.5; prior to version 11.5 the PatchFinder.exe is limited to only showing one web adaptor even though the patch has been applied to all web adaptors. The Patch Notification tool does not currently support showing patch notifications for the ArcGIS Web Adaptor (IIS).

As a best practice, clear the browser cache and re-launch the browser after installing the patch.

This patch can be uninstalled as outlined in the Uninstalling this patch on Windows .

Additionally, Esri recommends developing a rollback plan before installing patches. This may be taking a snapshot of machines and related file servers or using the WebGIS DR tool as a software backup. See Back up and restore best practices for more information. For those utilizing a highly available environment, refer to the help topic on how to apply patches in a highly available environment for guidance.

October 20, 2025:  A separate patch for Portal for ArcGIS 11.3 will soon be released to address this related defect: BUG-000168562 – “When using Map Viewer with HTTP/2 enabled on Internet Information Services (IIS) and in a Chrome or Edge browser, a burst of concurrent requests, such as rapid panning and zooming of the map, can lead to disappearing features and ERR_CONNECTION_RESET errors in the developer tools' console tab”.

• BUG-000177402 - When HTTP/2 is enabled on IIS, a burst of concurrent requests sent through the ArcGIS Web Adaptor (IIS) may lead to increased latency and rejected requests that return an HTTP 500 error.

On Windows, the release date order of the patches does not matter when installing multiple patches. If an older patch is installed after a newer patch, the newer patch takes precedence and the fixes from the newer patch will remain. 

The ArcGIS product listed in the table must be installed on your system before you can install a patch. Each patch setup is specific to the ArcGIS product in the list. To determine which products are installed on your system, please see the How to identify which ArcGIS products are installed section. Esri recommends that you install the patch for each product that is on your system.

Step 1: Download the appropriate file to a location other than your ArcGIS installation location.

Step 2: Make sure you have write access to your ArcGIS installation location.

Step 3: Double-click ArcGIS-<Version>-WAI-S-Patch.msp to start the setup process.

NOTE: If double clicking on the msp file does not start the setup installation, you can start the setup installation manually by using the following command:

Step 4: As a best practice, clear the browser cache and re-launch the browser after installing the patch.

To uninstall this patch on Windows, open the Windows Control Panel and navigate to installed programs. Make sure that "View installed updates" (upper left side of the Programs and Features dialog) is active. Select the patch name from the programs list and click Uninstall to remove the patch.

To determine which ArcGIS products are installed, choose the appropriate version of the PatchFinder utility for your environment and run it from your local machine. PatchFinder will list all products, hot fixes, and patches installed on your local machine.

PatchFinder for Windows