673 (Weakness Class)

Consider a blog publishing tool, which might have three explicit control spheres: the creation of articles, only accessible to a "publisher;" commenting on articles, only accessible to a "commenter" who is a registered user; and reading articles, only accessible to an anonymous reader. Suppose that the application is deployed on a web server that is shared with untrusted parties. If a local user can modify the data files that define who a publisher is, then this user has modified the control sphere. In this case, the issue would be resultant from another weakness such as insufficient permissions.

In Untrusted Search Path (CWE-426), a user might be able to define the PATH environment variable to cause the product to search in the wrong directory for a library to load. The product's intended sphere of control would include "resources that are only modifiable by the person who installed the product." The PATH effectively changes the definition of this sphere so that it overlaps the attacker's sphere of control.

A "control sphere" is a set of resources and behaviors that are accessible to a single actor, or a group of actors. A product's security model will typically define multiple spheres, possibly implicitly. For example, a server might define one sphere for "administrators" who can create new user accounts with subdirectories under /home/server/, and a second sphere might cover the set of users who can create or delete files within their own subdirectories. A third sphere might be "users who are authenticated to the operating system on which the product is installed." Each sphere has different sets of actors and allowable behaviors.

Architecture and Design