Authentication Bypass by Assumed-Immutable Data

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

In the following example, an "authenticated" cookie is used to determine whether or not a user should be granted access to a system.

boolean authenticated = new Boolean(getCookieValue("authenticated")).booleanValue();
if (authenticated) {
  ...
}

Modifying the value of a cookie on the client-side is trivial, but many developers assume that cookies are essentially immutable.

See Also