IIS 7.5 maxQueryStringLength configuration question

Question

We have a Windows 2008 R2 server running IIS 7.5.

Applications running inside are occasionally making GET requests to themselves with a rather long parameter list (up to 3000 chars) and this, when rdp:ed to the server itself and triggered in a browser, Firefox yields the IIS blue error screen :

HTTP Error 404.15 - "The request filtering module is configured to deny a request where the query string is too long. Verify the configuration/system.webServer/security/requestFiltering/requestLimits@maxQueryString setting in the applicationhost.config or web.config file"

I tried:

1. IIS manager
2. default web site
3. Request Filtering
4. Url
5. Edit feature settings
6. Max query string: from 2048 to something higher.

As a result, firefox shows

"Server error in "/" Application in red and "The length of the query string for this request exceeds the configured maxQueryStringLength value."

sys32/inetsrv/config/applicationHost.config is edited with:

    <requestLimits maxQueryString="4096" />
    </requestFiltering>

I also tried to manually edit web.config like that:

    <security>
    <requestFiltering>
    <requestLimits maxQueryString="3000" maxUrl="1000" />
    </requestFiltering>
    </security>

Result: Same as in 1, which is not the blue IIS error screen.

Both changes: Same is in 1 and 2.

My questions are:

1. As soon as I change the URL length or querystring params in the IIS manager or in web.config manually the error screen on the webserver turns from blue to the red-white-yellow Server Error in "/" Application, is this expected?

2. How can I make the IIS accept longer than 2048 bytes (the default) query strings in GET requests, if at all possible?

I understand that browsers have their own restrictions but only IE should have the ~2000 chars limit (it truncates the rest from the address field). This seems to be an issue with the IIS server.

Answer 1

Did you also configure it in the httpRuntime of your web.config file?

https://docs.microsoft.com/en-us/previous-versions/dotnet/netframework-4.0/e1f13641(v=vs.100)

<configuration> <system.web> <httpRuntime maxQueryStringLength="4000" /> </system.web> </configuration>