Critical Public Variable Without Final Modifier

Draft Variant

Structure: Simple

Description

The product has a critical public variable that is not final, which allows the variable to be modified to contain unexpected values.

Extended Description

If a field is non-final and public, it can be changed once the value is set by any function that has access to the class which contains the field. This could lead to a vulnerability if other parts of the program make assumptions about the contents of that field.

Common Consequences 2

Scope: Integrity

Impact: Modify Application Data

The object could potentially be tampered with.

Scope: Confidentiality

Impact: Read Application Data

The object could potentially allow the object to be read.

Detection Methods 1

Automated Static AnalysisHigh

Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc.)

Potential Mitigations 1

Phase: Implementation

Declare all public fields as final when possible, especially if it is used to maintain internal state of an Applet or of classes used by an Applet. If a field must be public, then perform all appropriate sanity checks before accessing the field from your code.

Demonstrative Examples 2

Suppose this WidgetData class is used for an e-commerce web site. The programmer attempts to prevent price-tampering attacks by setting the price of the widget using the constructor.

Code Example:Bad
Java
java

The price field is not final. Even though the value is set by the constructor, it could be modified by anybody that has access to an instance of WidgetData.

Assume the following code is intended to provide the location of a configuration file that controls execution of the application.

Code Example:Bad
C++
c++

Code Example:Bad
Java
java

While this field is readable from any function, and thus might allow an information leak of a pathname, a more serious problem is that it can be changed by any function.

References 1

Seven Pernicious Kingdoms: A Taxonomy of Software Security Errors

Katrina Tsipenyuk, Brian Chess, and Gary McGraw

NIST Workshop on Software Security Assurance Tools Techniques and Metrics • NIST

07-11-2005

https://samate.nist.gov/SSATTM_Content/papers/Seven%20Pernicious%20Kingdoms%20-%20Taxonomy%20of%20Sw%20Security%20Errors%20-%20Tsipenyuk%20-%20Chess%20-%20McGraw.pdf

ID: REF-6

Likelihood of Exploit

High

Applicable Platforms

Languages:

Java : UndeterminedC++ : Undetermined

Modes of Introduction

Implementation

Related Weaknesses

ChildOf:

Exposure of Resource to Wrong Sphere (CWE-668)

Taxonomy Mapping

7 Pernicious Kingdoms
CLASP
The CERT Oracle Secure Coding Standard for Java (2011)
Software Fault Patterns