COMMON WEAKNESS ENUMERATIONDraft

CWE-470

Use of Externally-Controlled Input to Select Classes or Code ('Unsafe Reflection')

The product uses external input with reflection to select which classes or code to use, but it does not sufficiently prevent the input from selecting improper classes or code.

Abstraction

Base

Structure

Simple

Likelihood of Exploit

Medium

Understand the problem

What is the problem?

The product uses external input with reflection to select which classes or code to use, but it does not sufficiently prevent the input from selecting improper classes or code.

Extended description

If the product uses external inputs to determine which class to instantiate or which method to invoke, then an attacker could supply values to select unexpected classes or methods. If this occurs, then the attacker could create control flow paths that were not intended by the developer. These paths could bypass authentication or access control checks, or otherwise cause the product to behave in an unexpected manner. This situation becomes a doomsday scenario if the attacker can upload files into a location that appears on the product's classpath (CWE-427) or add new entries to the product's classpath (CWE-426). Under either of these conditions, the attacker can use reflection to introduce new, malicious behavior into the product.

Terminology

Alternate terms and usages

Reflection Injection

Root cause

How and when does the problem arise?

Lifecycle phase

Architecture and Design

Lifecycle phase

Implementation

Risk

What does successful exploitation lead to?

Execute Unauthorized Code or CommandsAlter Execution Logic

Affected security scopes: Integrity, Confidentiality, Availability, Other

The attacker might be able to execute code that is not directly accessible to the attacker. Alternately, the attacker could call unexpected code in the wrong place or the wrong time, possibly modifying critical system state.
DoS: Crash, Exit, or RestartOther

Affected security scopes: Availability, Other

The attacker might be able to use reflection to call the wrong code, possibly with unexpected arguments that violate the API (CWE-227). This could cause the product to exit or hang.
Read Application Data

Affected security scopes: Confidentiality

By causing the wrong code to be invoked, the attacker might be able to trigger a runtime error that leaks sensitive information in the error message, such as CWE-536.

Defence

How is it prevented and fixed?

Architecture and Design

Architecture and design approach

Detail
Refactor your code to avoid using reflection.

Architecture and Design

Architecture and design approach

Detail
Do not use user-controlled inputs to select and load classes or code.

Implementation

Implementation-phase defence

Detail
Apply strict input validation by using allowlists or indirect selection to ensure that the user is only selecting allowable classes or code.

Verification

How is it detected?

Automated Static Analysis

High
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.)