Missing Handler

Description

When an exception is thrown and not caught, the process has given up an opportunity to decide if a given failure or event is worth a change in execution.

Demonstrations

The following examples help to illustrate the nature of this weakness and describe methods or techniques which can be used to mitigate the risk.

Note that the examples here are by no means exhaustive and any given weakness may have many subtle varieties, each of which may require different detection methods or runtime controls.

Example One

If a Servlet does not catch all exceptions, it may reveal debugging information that will help an adversary form a plan of attack. In the following method a DNS lookup failure will cause the Servlet to throw an exception.

protected void doPost (HttpServletRequest req, HttpServletResponse res) throws IOException {
  String ip = req.getRemoteAddr();
  InetAddress addr = InetAddress.getByName(ip);
  ...
  out.println("hello " + addr.getHostName());
}

When a Servlet throws an exception, the default error response the Servlet container sends back to the user typically includes debugging information. This information is of great value to an attacker.

See Also