When a SAM dispatches to a simple Servlet via an include, then after the SAM returns SUCCESS and the requested Servlet should be loaded, Undertow instead loads the include again.

For example, consider a request to a public Servlet mapped to /servlet, another Servlet mapped to /includedServlet and a SAM with the following code:

HttpServletRequest request = (HttpServletRequest) messageInfo.getRequestMessage();
HttpServletResponse response = (HttpServletResponse) messageInfo.getResponseMessage();

request.getRequestDispatcher("/includedServlet")
       .include(request, response);

CallerPrincipalCallback(clientSubject, (Principal) null) });

return SUCCESS;

After this SAM has executed, Undertow will proceed to invoke /includedServlet for a second time instead of invoking the expected /servlet

A reproducer is available here: https://github.com/javaee-samples/javaee7-samples/tree/master/jaspic/dispatching