The software does not restrict or incorrectly restricts access to a resource from an unauthorized actor.
Access control involves the use of several protection mechanisms such as authentication (proving the identity of an actor) authorization (ensuring that a given actor can access a resource), and accountability (tracking of activities that were performed). When any mechanism is not applied or otherwise fails, attackers can compromise the security of the software by gaining privileges, reading sensitive information, executing commands, evading detection, etc.
There are two distinct behaviors that can introduce access control weaknesses:
Specification: incorrect privileges, permissions, ownership, etc. are explicitly specified for either the user or the resource (for example, setting a password file to be world-writable, or giving administrator capabilities to a guest user). This action could be performed by the program or the administrator.
Enforcement: the mechanism contains errors that prevent it from properly enforcing the specified access control requirements (e.g., allowing the user to specify their own privileges, or allowing a syntactically-incorrect ACL to produce insecure settings). This problem occurs within the program itself, in that it does not actually enforce the intended security policy that the administrator specifies.
The terms "access control" and "authorization" are often used
interchangeably, although many people have distinct definitions. The CWE
usage of "access control" is intended as a general term for the various
mechanisms that restrict which users can access which resources, and
"authorization" is more narrowly defined. It is unlikely that there will
be community consensus on the use of these terms.
Time of Introduction
Architecture and Design
Technical Impact: Varies by context
Phases: Architecture and Design; Operation
Very carefully manage the setting, management, and handling of
privileges. Explicitly manage trust zones in the software.
Phase: Architecture and Design
Strategy: Separation of Privilege
Compartmentalize the system to have "safe" areas where trust
boundaries can be unambiguously drawn. Do not allow sensitive data to go
outside of the trust boundary and always be careful when interfacing
with a compartment outside of the safe area.
Ensure that appropriate compartmentalization is built into the system
design and that the compartmentalization serves to allow for and further
reinforce privilege separation functionality. Architects and designers
should rely on the principle of least privilege to decide when it is
appropriate to use and to drop system privileges.