Execution After Redirect (EAR)

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

This code queries a server and displays its status when a request comes from an authorized IP address.

$requestingIP = $_SERVER['REMOTE_ADDR'];
if(!in_array($requestingIP,$ipAllowList)){
  echo "You are not authorized to view this page";
  http_redirect($errorPageURL);
}
$status = getServerStatus();
echo $status;
...

This code redirects unauthorized users, but continues to execute code after calling http_redirect(). This means even unauthorized users may be able to access the contents of the page or perform a DoS attack on the server being queried. Also, note that this code is vulnerable to an IP address spoofing attack (CWE-212).

See Also