CWE-454: External Initialization of Trusted Variables
External Initialization of Trusted Variables
Weakness ID: 454 (Weakness Base)
Status: Draft
Description
Description Summary
The software initializes critical internal variables using
inputs that can come from externally controlled sources.
Extended Description
A software system should be reluctant to trust variables that have been
initialized outside of its trust boundary, especially if they are
initialized by users. They may have been initialized incorrectly. If an
attacker can initialize the variable, then he/she can influence what the
vulnerable system will do.
Time of Introduction
Architecture and Design
Implementation
Applicable Platforms
Languages
PHP: (Sometimes)
All
Platform Notes
This is often found in PHP due to register_globals and the common practice
of storing library/include files under the web document root so that they
are available using a direct request.
Demonstrative Examples
Example 1
In the Java example below, a system property controls the debug
level of the application. If an attacker is able to modify the system
property, he may be able to coax the application into divulging sensitive
information by virtue of the fact that additional debug information is
printed/exposed as the debug level increases.
(Bad Code)
Java
int debugLevel =
Integer.getInteger("com.domain.application.debugLevel").intValue();
Specify arbitrary modules using environment
variable.
Potential Mitigations
Phase
Description
A software system should be reluctant to trust variables that have
been initialized outside of its trust boundary. Ensure adequate checking
(e.g. input validation) is performed when relying on input from outside
a trust boundary.
Architecture and Design
Avoid any external control of variables. If necessary, restrict the
variables that can be modified using a whitelist, and use a different
namespace or naming convention if possible.
Description
