 <p>I had a similar issue. In my case it was the client system that had a virus scanner installed. Those scanners sometimes have identity theft modules that intercept <code>POST</code>s, scan the body and then pass it on.</p> <p>In my case <code>BitDefender</code> cached about 5MB before passing it on.</p> <p>If the whole payload was less then the <code>POST</code> was delivered as non chunked fixed length request.</p>