Comparison of Classes by Name

Draft Variant

Structure: Simple

Description

This vulnerability occurs when an application determines an object's trustworthiness or behavior solely by checking its class name. Since multiple classes can share identical names across different packages or classloaders, this comparison can lead to using the wrong, potentially malicious, class.

Extended Description

Relying on class name strings for security decisions is inherently risky. Attackers can craft classes with names identical to your trusted ones, tricking your application into granting them unauthorized privileges or executing unintended code paths. This is especially problematic in environments with multiple classloaders, like application servers, where the same fully-qualified name can point to completely different implementations. Detecting these logical flaws manually is challenging, as they depend on runtime context. While SAST tools can flag dangerous comparison patterns, Plexicus uses AI to not only identify the risk but also suggest specific, secure refactoring—such as using direct class object comparisons or verifying the classloader—saving significant manual review time and preventing impersonation attacks.

Common Consequences 1

Scope: IntegrityConfidentialityAvailability

Impact: Execute Unauthorized Code or Commands

If a product relies solely on the name of an object to determine identity, it may execute the incorrect or unintended code.

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

Use class equivalency to determine type. Rather than use the class name to determine if an object is of a given type, use the getClass() method, and == operator.

Demonstrative Examples 2

In this example, the expression in the if statement compares the class of the inputClass object to a trusted class by comparing the class names.

Code Example:

Bad

Java

java

// Do something assuming you trust inputClass*

java

However, multiple classes can have the same name therefore comparing an object's class by name can allow untrusted classes of the same name as the trusted class to be use to execute unintended or incorrect code. To compare the class of an object to the intended class the getClass() method and the comparison operator "==" should be used to ensure the correct trusted class is used, as shown in the following example.

Code Example:

Good

Java

java

// Do something assuming you trust inputClass*

java

In this example, the Java class, TrustedClass, overrides the equals method of the parent class Object to determine equivalence of objects of the class. The overridden equals method first determines if the object, obj, is the same class as the TrustedClass object and then compares the object's fields to determine if the objects are equivalent.

Code Example:

Bad

Java

java

// first check to see if the object is of the same class* if (obj.getClass().getName().equals(this.getClass().getName())) { ```

java

However, the equals method compares the class names of the object, obj, and the TrustedClass object to determine if they are the same class. As with the previous example using the name of the class to compare the class of objects can lead to the execution of unintended or incorrect code if the object passed to the equals method is of another class with the same name. To compare the class of an object to the intended class, the getClass() method and the comparison operator "==" should be used to ensure the correct trusted class is used, as shown in the following example.

Code Example:

Good

Java

java

// first check to see if the object is of the same class* if (obj.getClass() == this.getClass()) { ``` ... } ... }

References 2

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

The CLASP Application Security Process

Secure Software, Inc.

2005

https://cwe.mitre.org/documents/sources/TheCLASPApplicationSecurityProcess.pdf(2024-11-17)

ID: REF-18

Likelihood of Exploit

High

Applicable Platforms

Languages:

Java : Undetermined

Modes of Introduction

Implementation

Related Weaknesses

ChildOf:

Comparison Using Wrong Factors (CWE-1025)

Taxonomy Mapping

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