IIS 8.5 Internal error 500.19 - iis

Question

I have Basic Auth enabled for the specific folder and anonymous disabled. I also have created users, however I get a "The page cannot be displayed because an internal server error has occurred." message on the browser. Here is the log from the failed request tracing. I have been looking at this for hours but not been able to solve it.
The same error triggers when I access any non existing page, for example http://144.144.144.144/adas
<failedRequest url="http://144.144.144.144:80/adas"
siteId="1"
appPoolId="DefaultAppPool"
processId="824"
verb="GET"
remoteUserName=""
userName=""
tokenUserName="NT AUTHORITY\IUSR"
authenticationType="anonymous"
activityId="{80000068-0002-FF00-B63F-84710C7967BB}"
failureReason="STATUS_CODE"
statusCode="500.19"
triggerStatusCode="500.19"
timeTaken="0"
xmlns:freb="http://schemas.microsoft.com/win/2006/06/iis/freb"
>
the log for the basic auth:
<?xml version="1.0" encoding="UTF-8" ?>
<?xml-stylesheet type='text/xsl' href='freb.xsl'?>
<!-- saved from url=(0014)about:internet -->
<failedRequest url="http://144.144.144.144:80/admin/"
siteId="1"
appPoolId="DefaultAppPool"
processId="820"
verb="GET"
authenticationType="NOT_AVAILABLE" activityId="{8000000E-0002-FF00-B63F-84710C7967BB}"
failureReason="STATUS_CODE"
statusCode="500.19"
triggerStatusCode="500.19"
timeTaken="0"
xmlns:freb="http://schemas.microsoft.com/win/2006/06/iis/freb"
>
<Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
<System>
<Provider Name="WWW Server" Guid="{3A2A4E84-4C21-4981-AE10-3FDA0D9B0F83}"/>
<EventID>0</EventID>
<Version>1</Version>
<Level>0</Level>
<Opcode>1</Opcode>
<Keywords>0x0</Keywords>
<TimeCreated SystemTime="2016-09-29T15:24:04.662Z"/>
<Correlation ActivityID="{8000000E-0002-FF00-B63F-84710C7967BB}"/>
<Execution ProcessID="820" ThreadID="3756"/>
<Computer>OWNEROR-9DTV6I9</Computer>
</System>
<EventData>
<Data Name="ContextId">{8000000E-0002-FF00-B63F-84710C7967BB}</Data>
<Data Name="SiteId">1</Data>
<Data Name="AppPoolId">DefaultAppPool</Data>
<Data Name="ConnId">1610612749</Data>
<Data Name="RawConnId">0</Data>
<Data Name="RequestURL">http://144.144.144.144:80/admin/</Data>
<Data Name="RequestVerb">GET</Data>
</EventData>
<RenderingInfo Culture="el-GR">
<Opcode>GENERAL_REQUEST_START</Opcode>
</RenderingInfo>
<ExtendedTracingInfo xmlns="http://schemas.microsoft.com/win/2004/08/events/trace">
<EventGuid>{D42CF7EF-DE92-473E-8B6C-621EA663113A}</EventGuid>
</ExtendedTracingInfo>
</Event>
<Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
<System>
<Provider Name="WWW Server" Guid="{3A2A4E84-4C21-4981-AE10-3FDA0D9B0F83}"/>
<EventID>0</EventID>
<Version>1</Version>
<Level>0</Level>
<Opcode>33</Opcode>
<Keywords>0x0</Keywords>
<TimeCreated SystemTime="2016-09-29T15:24:04.662Z"/>
<Correlation ActivityID="{8000000E-0002-FF00-B63F-84710C7967BB}"/>
<Execution ProcessID="820" ThreadID="3756"/>
<Computer>OWNEROR-9DTV6I9</Computer>
</System>
<EventData>
<Data Name="ContextId">{8000000E-0002-FF00-B63F-84710C7967BB}</Data>
<Data Name="HttpStatus">500</Data>
<Data Name="HttpSubStatus">19</Data>
<Data Name="FileNameOrURL"></Data>
</EventData>
<RenderingInfo Culture="el-GR">
<Opcode>GENERAL_SEND_CUSTOM_ERROR</Opcode>
</RenderingInfo>
<ExtendedTracingInfo xmlns="http://schemas.microsoft.com/win/2004/08/events/trace">
<EventGuid>{D42CF7EF-DE92-473E-8B6C-621EA663113A}</EventGuid>
</ExtendedTracingInfo>
</Event>
<Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
<System>
<Provider Name="WWW Server" Guid="{3A2A4E84-4C21-4981-AE10-3FDA0D9B0F83}"/>
<EventID>0</EventID>
<Version>1</Version>
<Level>0</Level>
<Opcode>2</Opcode>
<Keywords>0x0</Keywords>
<TimeCreated SystemTime="2016-09-29T15:24:04.662Z"/>
<Correlation ActivityID="{8000000E-0002-FF00-B63F-84710C7967BB}"/>
<Execution ProcessID="820" ThreadID="3756"/>
<Computer>OWNEROR-9DTV6I9</Computer>
</System>
<EventData>
<Data Name="ContextId">{8000000E-0002-FF00-B63F-84710C7967BB}</Data>
<Data Name="BytesSent">222</Data>
<Data Name="BytesReceived">466</Data>
<Data Name="HttpStatus">500</Data>
<Data Name="HttpSubStatus">19</Data>
</EventData>
<RenderingInfo Culture="el-GR">
<Opcode>GENERAL_REQUEST_END</Opcode>
</RenderingInfo>
<ExtendedTracingInfo xmlns="http://schemas.microsoft.com/win/2004/08/events/trace">
<EventGuid>{D42CF7EF-DE92-473E-8B6C-621EA663113A}</EventGuid>
</ExtendedTracingInfo>
</Event>
</failedRequest>
The server specs are: 64bit Windows 2012 R2 with IIS 8.5. Does someone know what is going on ? Thank you in advance.

Answer 1

it seems the following lines in web.config caused the trouble. still don't know why.
<httpErrors errorMode="DetailedLocalOnly">
<remove statusCode="404" subStatusCode="-1" />
<error statusCode="404" prefixLanguageFilePath="" path="C:\inetpub\wwwroot\notfound.htm" responseMode="File" />
</httpErrors>
I resolved the problem by deleting those four lines.

Answer 2

The error message itself should be "Absolute physical path ... is not allowed in system.webServer/httpErrors section in web.config file. Use relative path instead."
And that clearly tells both the cause and the solution. That value set to path must be a relative path.
You can check the reference below for example,
https://www.iis.net/configreference/system.webserver/httperrors/error

Answer 3

I ran into this issue myself and found that a "bad character" had crept into my file. My 500.19 error was telling me that the XML header itself, <?xml version="1.0" encoding="UTF-8" ?>, was causing the web.config to be "malformed XML".
Deleting the line in notepad and resaving fixed the issue, but why would the XML header cause a malformed XML error!? So I went back to Stash's Web UI to view the file to see if it had changed in source.
That was where I noted a red dot as the first character of the file, on the same line as the XML header. The red dot is usually a 'bad character', someone used an editor that allowed a character from outside the file's encoding or maybe a corrupted save. But what you end up with is an invisible character that breaks IIS when it goes to read your config!
SO, be careful not to throw the baby out with the bath water! It might not be what you SEE that's wrong.
In windows, a quick fix for bad characters is to use clipboard's "dumbness" (strictness) and do a Ctrl-A, Ctrl-C, delete the file, create an empty file with the same name, and Ctrl-V. Notepad works nicely with this as it won't try to "help" with additional interpretation when you paste back. This will effectively and quickly remove any "invisible" characters that Windows doesn't recognize, since the clipboard simply won't copy them!
Though untested, mismatched encoding values in the XML headers among your other .config files (machine.config, app.configs, etc.) might lead to this kind of an issue, too. It has been noted that IIS won't respect different encodings as it reads all the .configs together. Currently it defaults to UTF-8 (ASP NET 4), so if you change your XML encoding in your web.config for some reason, make sure your machine.config matches. I feel I should call out here that changing your encoding away from the default is risky, so don't do it if you can help it!