Hi

I'm using Umbraco version 7.2.2 assembly: 1.0.5529.18522 on a Windows 2012 server with IIS 8.5.

After we started getting some load on the servers we sterted to see this error in the windows application log:

Faulting application name: w3wp.exe, version: 8.5.9600.16384, time stamp: 0x5215df96
Faulting module name: ntdll.dll, version: 6.3.9600.17736, time stamp: 0x550f4336
Exception code: 0xc0000374
Fault offset: 0x00000000000f0f20
Faulting process id: 0x5944
Faulting application start time: 0x01d09cad7e0cc476
Faulting application path: c:\windows\system32\inetsrv\w3wp.exe
Faulting module path: C:\Windows\SYSTEM32\ntdll.dll
Report Id: 99f0ac38-08a5-11e5-80c4-00155d0ea910
Faulting package full name: 
Faulting package-relative application ID: 

and this in the windows system log:

 process serving application pool 'www.mydomain.com' suffered a fatal communication error with the Windows Process Activation Service. The process id was '22852'. The data field contains the error number.

Going through the crash dump I found that the error was a double free error on the heap. 

I had to get help form Microsoft support to find out where the error originated, and they found that the code that caused the error was this code in the UmbracoModule.cs file in the Umbraco.web project:

//disable asp.net headers (security)
app.PreSendRequestHeaders += (sender, args) =>
    {
        var httpContext = ((HttpApplication)sender).Context;
        try
        {
            httpContext.Response.Headers.Remove("Server");
            //this doesn't normally work since IIS sets it but we'll keep it here anyways.
            httpContext.Response.Headers.Remove("X-Powered-By");
        }
        catch (PlatformNotSupportedException ex)
        {
            // can't remove headers this way on IIS6 or cassini.
        }
    };

As Microsoft support explained "The Umbraco module is the one removing headers and it does it in PreSendRequestHeaders event. This event is not a good place to remove the headers."

I have tried removing this code an buld the umbraco .dll-files again and this removed the heap error. Unfortunatly it seams that this might have spawned a new error that I haven't quite managed to pinpoint yet, but I suspect that I introduces some new error in the dll because they werent buildt correct.

So I'm wondering about two things.

1. Could someone help me build correct dll-files with the code above which removes the headers?
2. If this is something that can cause this kind of error, who can look into it and remove them from future Umbraco releases?