Strangely I was dealing with a very similar issue and found an answer to my situation. In your case you have no origin. In my case I did have an origin but CORS was not working as I expected. Once you get your origin sorted out, you'll probably still have a similar issue to mine where CORS still won't work even though you configured it. The solution I came across was to update the web.config:
<system.webServer>
<httpProtocol>
<customHeaders>
<add name="Access-Control-Allow-Origin" value="*" />
<add name="Access-Control-Allow-Headers" value="Content-Type" />
<add name="Access-Control-Allow-Methods" value="GET, POST, PUT, DELETE, OPTIONS" />
</customHeaders>
</httpProtocol>
</system.webServer>
This worked for me.