A WCF request with "Expect: 100-continue" header returns a 400 bad request. It is happening only TLS 1.3

Jenus M 6 Reputation points
2022-09-12T06:42:00.297+00:00

A WCF request with "Expect: 100-continue" header returns a 400 bad request and it is happening only in TLS 1.3 connection. The same request works fine with TLS 1.2.

Incase of TLS 1.3, the request works fine if the request header don't have "Expect: 100-continue" header. So the "Expect: 100-continue" header is playing something in TLS 1.3.

Please help.

.NET
.NET
Microsoft Technologies based on the .NET software framework.
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Windows 11
Windows 11
A Microsoft operating system designed for productivity, creativity, and ease of use.
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  1. Limitless Technology 39,301 Reputation points
    2022-09-12T19:52:59.87+00:00

    Hello there,

    Windows do not fully support TLS 1.3 yet. Some versions are supported, but you'll need to upgrade your Windows to the available version if you want to try it out. As this occurs only in TLS 1.3 you can try to set the trace configuration to the WCF service. Then we can catch the more detailed error message. That will help us to find the root issue.

    Meanwhile, you can look into this thread with a similar discussion.

    How to enable Tls version 1.3 for both WCF service and WCF client application https://learn.microsoft.com/en-us/answers/questions/951823/how-to-enable-tls-version-13-for-both-wcf-service.html

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