IIS Error 401.0 - Unauthorized after upgrade to Windows 11

Luis 126

Hello everyone. I have an old intranet website that is currently working on Windows Server 2019. The site is an ASP.Net Web App using .Net Framework 4.7.2. I need to make minor cosmetic changes to it. When I test the source code on VS2019 or VS2022 it works fine, when I publish to my local IIS or the 2019 server, I get error "401.0 Unauthorized".

I'm using Anonymous Authentication, the DefaultAppPool has Write, Read and Execute access to the root folder where the site has been published. DefaultAppPool uses ApplicationPoolIdentity. Same settings are in the working site that is on the server. I tried to create a trace, but it says 401.0 is not a valid code, I use a range from 400 to 500.1 and did not write anything on the log. Fiddler didn't help much either.

If I create a new demo site and publish it in both my local computer and the server, it works fine. Is there anything else that I can do to correct this issue?

Thank you.

Luis

Lex Li (Microsoft) 4,742 Reputation points Microsoft Employee

2024-03-07T22:53:50.9833333+00:00

401.0 is not a typical IIS/ASP.NET error code, so no wonder you found it difficult to locate useful resources. If possible, we might start from the error page itself.

You can post a full screen shot so that we can see if the page itself has any more hints to guide us.

Fiddler can be helpful by showing you the HTTP response message with all details, so you might open the raw view and take a screenshot as well to share here.

You must mask out confidential information such as IP addresses whenever needed.
Sam Wu-MSFT 7,036 Reputation points Microsoft Vendor

2024-03-08T03:24:53.9066667+00:00

@Luis

It is difficult to reproduce your problem based on your description, what trace did you create? If it is a failed request tracking, please post the content of the error message, if not, you can try using failed request tracing to see details about 401 error, this will generate detail log file, which will help you to identify the problem.
Luis 126 Reputation points

2024-03-08T13:40:42.71+00:00

@Lex Li (Microsoft) Thank you for replying, these are the screenshots of the error message and the response header from Fiddler.

Thank you!
Luis 126 Reputation points

2024-03-08T14:12:14.1233333+00:00

@Sam Wu-MSFT Thank you for replying, I posted the error message on the previous message, I enabled a trace, and got an XML file with 4000+ lines, but I did not see anything that could indicate an issue.

Thanks!

1 answer

Luis 126 Reputation points

2024-03-08T16:21:35.12+00:00
Thanks @Lex Li (Microsoft) and @Sam Wu-MSFT , I found the culprit for this issue. The line shown below was at the top of my HomeControler. This was a leftover code from when this app was running on Azure at one point, in other words, my fault.

Thank you.

[System.Web.Mvc.Authorize]
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1 person found this answer helpful.
Lex Li (Microsoft) 4,742 Reputation points Microsoft Employee

2024-03-08T23:10:04.0633333+00:00

Glad to see you found the culprit. Just some hints to help you in the future. The error page shows a typical pattern, with "Module" as "ManagedPipelineHandler", "Handler" as "System.Web.Mvc.MvcHandler". That pattern indicates the request has entered ASP.NET 4.x processing pipeline (beyond common IIS modules), and the status code 401 is likely returned from a piece of ASP.NET code (either yours, or from within the framework). That matches your finding, a method was protected by the Authorize attribute.
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