How do you prevent CWE-493?

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.

How is CWE-493 detected?

Automated Static Analysis: 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.)

What are the consequences of CWE-493?

Exploiting CWE-493 can lead to: Modify Application Data, Read Application Data.

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CWE-493: Critical Public Variable Without Final Modifier

Variant weakness

Draft

CWE-493: Critical Public Variable Without Final Modifier

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

Last updated May 1, 2026

Recorded CVEs

With this primary weakness

KEVs

In the CISA KEV catalog

High

Likelihood of exploit

Per MITRE

Variant

Abstraction

MITRE classification

Overview

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.

Background

Mobile code, such as a Java Applet, is code that is transmitted across a network and executed on a remote machine. Because mobile code developers have little if any control of the environment in which their code will execute, special security concerns become relevant. One of the biggest environmental threats results from the risk that the mobile code will run side-by-side with other, potentially malicious, mobile code. Because all of the popular web browsers execute code from multiple sources together in the same JVM, many of the security guidelines for mobile code are focused on preventing manipulation of your objects' state and behavior by adversaries who have access to the same virtual machine where your program is running.

Final provides security by only allowing non-mutable objects to be changed after being set. However, only objects which are not extended can be made final.

Common consequences

What can happen when CWE-493 is exploited.

Modify Application Data

Affects: Integrity

The object could potentially be tampered with.

Read Application Data

Affects: Confidentiality

The object could potentially allow the object to be read.

How it happens

When it is introduced

Typically introduced during these phases of the software lifecycle.

Code examples

MITRE examples of the weakness in code.

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.

Vulnerable example

java

public final class WidgetData extends Applet {

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.

Vulnerable example

cpp

public string configPath = "/etc/application/config.dat";

Vulnerable example

java

public String configPath = new String("/etc/application/config.dat");

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.

CWE-493: Critical Public Variable Without Final Modifier

Overview

Background

Common consequences

How it happens

When it is introduced

Applies to

How to prevent it

How to detect it

Automated Static Analysis

Code examples

Terminology & mappings

Mapped taxonomies

Frequently asked questions

References

Track CWE-493 CVEs

Overview

Background

Common consequences

How it happens

When it is introduced

Applies to

How to prevent it

How to detect it

Automated Static Analysis

Code examples

Related weaknesses

Parent

Child

Terminology & mappings

Mapped taxonomies

Frequently asked questions

References

Track CWE-493 CVEs