KB5066835 update causing IIS Service to not work

Sashi Kumar 405 Reputation points
2025-10-15T10:06:37.1166667+00:00

Recently my local hosted IIS services is not running after the new update. My visual studio projects also can't be run as well. I have to delete the new update in order to run my projects and local hosted services again. May I know what is the problem?

Developer technologies | ASP.NET Core | Other

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Answer accepted by question author
xavier ubikos 175 Reputation points
2025-10-16T05:23:40.57+00:00

Hi there!

This morning there was a Defender update, I have installed it an now it works!!!

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  1. Dave Payne 10 Reputation points
    2025-10-16T08:03:23.77+00:00

    This mornings security update (Security Intelligence Update for Microsoft Defender Antivirus - KB2267602 (Version 1.439.210.0) - Current Channel (Broad)) has fixed the issue. Installed updates again and then this and all OK now

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  2. Luca F 6 Reputation points
    2025-10-16T05:46:18.3266667+00:00

    We experienced the same issue. Installing today's update KB2267602 (Security Intelligence Update for Microsoft Defender Antivirus) resolved it for us after restarting the computer.

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  3. Alexander Avidan 5 Reputation points
    2025-10-15T22:42:42.58+00:00

    I uninstalled KB506683 and 5066835. that fixed the problem. And saved me from a heart attack...

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  4. John Hatton 25 Reputation points
    2025-10-15T21:04:06.3566667+00:00

    Not just an IIS problem. It's breaking our app on some subset of customer machines (and, luckily, mine). Minimal repro:

    using System;
using System.Net;
using System.Net.Http;
using System.Threading;
using System.Threading.Tasks;
class MinimalRepro
{
    static async Task Main()
    {
        var listener = new HttpListener();
        listener.Prefixes.Add("http://localhost:8089/");
        listener.Start();
        listener.BeginGetContext(ar =>
        {
            try
            {
                var context = listener.EndGetContext(ar); // FAILS HERE
                context.Response.StatusCode = 200;
                context.Response.Close();
            }
        }, null);
        await Task.Delay(200);
        // Trigger the error
        using var client = new HttpClient();
        await client.GetAsync("http://localhost:8089/");
        listener.Stop();
    }
}

    ERROR: 50 - The request is not supported.

    Unhandled exception. System.Net.Http.HttpRequestException: An error occurred while sending the request.

    ---> System.IO.IOException: Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host..

    ---> System.Net.Sockets.SocketException (10054): An existing connection was forcibly closed by the remote host.

    at System.Net.Sockets.Socket.AwaitableSocketAsyncEventArgs.CreateException(SocketError error, Boolean forAsyncThrow)

    at System.Net.Sockets.Socket.AwaitableSocketAsyncEventArgs.ReceiveAsync(Socket socket, CancellationToken cancellationToken)

    at System.Net.Sockets.Socket.ReceiveAsync(Memory`1 buffer, SocketFlags socketFlags, Boolean fromNetworkStream, CancellationToken cancellationToken)

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