CWE-493 Variante Borrador High likelihood

Critical Public Variable Without Final Modifier

This vulnerability occurs when a security-sensitive variable is declared as public but not marked as final, allowing untrusted code to unexpectedly change its value after initialization.

Definición

What is CWE-493?

This vulnerability occurs when a security-sensitive variable is declared as public but not marked as final, allowing untrusted code to unexpectedly change its value after initialization.
When a critical variable—like a security flag, configuration setting, or cryptographic key—is made public without the `final` modifier, any part of the application with access to its class can alter its contents. This breaks the intended design and can lead to security failures, as other components may rely on that value remaining constant after being set. Manually tracking these exposed variables across a large codebase is challenging. An ASPM like Plexicus can automatically detect this pattern via SAST, and its AI remediation engine can suggest the specific code change—such as adding the `final` keyword or refactoring to a private field—saving significant manual review time and reducing risk.
Impacto en el mundo real

Real-world CVEs caused by CWE-493

Todavía no hay CVEs públicos enlazados a esta CWE en el catálogo de MITRE.

Cómo lo explotan los atacantes

Ruta del atacante paso a paso

  1. 1

    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.

  2. 2

    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.

  3. 3

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

  4. 4

    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.

Ejemplo de código vulnerable

Vulnerable Java

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 Java 
public final class WidgetData extends Applet {
  	public float price;
  	...
  	public WidgetData(...) {
  		this.price = LookupPrice("MyWidgetType");
  	}
  }
Ejemplo de código seguro

Secure pseudo

Seguro pseudo 
// Validate, sanitize, or use a safe API before reaching the sink.
function handleRequest(input) {
  const safe = validateAndEscape(input);
  return executeWithGuards(safe);
}
What changed: the unsafe sink is replaced (or the input is validated/escaped) so the same payload no longer triggers the weakness.
Lista de prevención

How to prevent CWE-493

  • 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.
Señales de detección

How to detect CWE-493

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.)

Auto-corrección de Plexicus

Plexicus detecta automáticamente CWE-493 y abre un PR de corrección en menos de 60 segundos.

Codex Remedium escanea cada commit, identifica esta debilidad concreta y entrega un pull request listo para revisión con el parche. Sin tickets. Sin traspasos.

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Preguntas frecuentes

Frequently asked questions

¿Qué es CWE-493?

This vulnerability occurs when a security-sensitive variable is declared as public but not marked as final, allowing untrusted code to unexpectedly change its value after initialization.

¿Qué gravedad tiene CWE-493?

MITRE califica la probabilidad de explotación como Alta — esta debilidad se explota activamente en la práctica y debe priorizarse para su remediación.

¿Qué lenguajes o plataformas se ven afectados por CWE-493?

MITRE lists the following affected platforms: Java, C++.

¿Cómo puedo prevenir 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.

¿Cómo detecta y corrige Plexicus CWE-493?

El motor SAST de Plexicus detecta la firma de flujo de datos para CWE-493 en cada commit. Cuando hay coincidencia, nuestro agente Codex Remedium abre un PR de corrección con el código corregido, las pruebas y un resumen de una línea para el revisor.

¿Dónde puedo aprender más sobre CWE-493?

MITRE publica la definición canónica en https://cwe.mitre.org/data/definitions/493.html. También puedes consultar la documentación de OWASP y NIST para guías relacionadas.

Debilidades relacionadas

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Recursos

Further reading

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