'Where does a failed POST request 403 error appear in IIS 10 logs? What's the source of the error?

A POST request to the IIS 10 web server gets a 403 forbidden response. All other GET and POST requests work fine except for this one page. But in the IIS logs, that request doesn't appear--post requests from other pages do appear. We turned on failed request tracing, bounced IIS and tried again, but there's not any failed request trace log file.

The 403 response body has HTML so it must come from somewhere. Please suggest some idea to discover what's the source or cause of the 403?

<html>
<head><title>403 Forbidden</title></head>
<body bgcolor="white">
<center><h1>403 Forbidden</h1></center>
</body>
</html>
<!-- a padding to disable MSIE and Chrome friendly error page -->
<!-- a padding to disable MSIE and Chrome friendly error page -->
<!-- a padding to disable MSIE and Chrome friendly error page -->
<!-- a padding to disable MSIE and Chrome friendly error page -->
<!-- a padding to disable MSIE and Chrome friendly error page -->
<!-- a padding to disable MSIE and Chrome friendly error page -->
postiishttp-status-code-403iis-10


Solution 1:[1]

The response has this header "server: awselb/20" so this 403 forbidden response comes from an AWS Elastic Load Balancing server which probably has some security filtering of requests. Our AWS expert will look into it.

Sources

This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.

Source: Stack Overflow

Solution Source
Solution 1 Tiger Darling

Related Questions