CWE-496: Public Data Assigned to Private Array-Typed Field

Definición

What is CWE-496?

This vulnerability occurs when a developer stores sensitive data in a private array, but then assigns a publicly accessible reference to that same array. This effectively makes all the private array's contents available to unauthorized code, bypassing intended access controls.

When you declare an array field as `private`, you're telling the system that external code shouldn't directly access it. However, if you then assign a public variable or return value to point to that same private array, you've created a backdoor. Any code with access to the public reference can now read, modify, or delete the supposedly private data, completely undermining your encapsulation. To prevent this, never expose references to your private arrays. Instead, return copies (defensive copies) of the array data or use immutable collections. Always validate that your getter methods or public fields don't provide direct access to mutable private objects, as this is a common oversight that leads to serious data exposure.

Impacto en el mundo real

Real-world CVEs caused by CWE-496

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
Identifica una ruta de código que maneje entrada no confiable sin validación.
2
Crea un payload que ejercite el comportamiento inseguro — inyección, traversal, overflow o abuso de lógica.
3
Envía el payload a través de una solicitud normal y observa la reacción de la aplicación.
4
Itera hasta que la respuesta filtre datos, ejecute código del atacante o escale privilegios.

Ejemplo de código vulnerable

Vulnerable Java

In the example below, the setRoles() method assigns a publically-controllable array to a private field, thus allowing the caller to modify the private array directly by virtue of the fact that arrays in Java are mutable.

Vulnerable Java

private String[] userRoles;
  public void setUserRoles(String[] userRoles) {
  	this.userRoles = userRoles;
  }

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-496

Implementation Do not allow objects to modify private members of a class.

Señales de detección

How to detect CWE-496

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.)

CWE-496

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Preguntas frecuentes

Frequently asked questions

¿Qué es CWE-496?

This vulnerability occurs when a developer stores sensitive data in a private array, but then assigns a publicly accessible reference to that same array. This effectively makes all the private array's contents available to unauthorized code, bypassing intended access controls.

¿Qué gravedad tiene CWE-496?

MITRE no ha publicado una calificación de probabilidad de explotación para esta debilidad. Trátala como de impacto medio hasta que tu modelo de amenazas demuestre lo contrario.

¿Qué lenguajes o plataformas se ven afectados por CWE-496?

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

¿Cómo puedo prevenir CWE-496?

Do not allow objects to modify private members of a class.

¿Cómo detecta y corrige Plexicus CWE-496?

El motor SAST de Plexicus detecta la firma de flujo de datos para CWE-496 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-496?

MITRE publica la definición canónica en https://cwe.mitre.org/data/definitions/496.html. También puedes consultar la documentación de OWASP y NIST para guías relacionadas.

Debilidades relacionadas

Weaknesses related to CWE-496

CWE-664 Padre

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Plexicus es Proof-Driven AppSec: hallazgos validados, comprensión contextual y remediación revisada — anclada en evidencia, acotada contigo.

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Public Data Assigned to Private Array-Typed Field

What is CWE-496?

Real-world CVEs caused by CWE-496

Ruta del atacante paso a paso

Vulnerable Java

Secure pseudo

How to prevent CWE-496

How to detect CWE-496

Don't catalog this weakness. Prove it's reachable.

Frequently asked questions

Weaknesses related to CWE-496

Improper Control of a Resource Through its Lifetime

Incorrect Access of Indexable Resource ('Range Error')

Creation of Emergent Resource

Improper Preservation of Consistency Between Independent Representations of Shared State

Reliance on Component That is Not Updateable

Information Loss or Omission

Incomplete Internal State Distinction

Uncontrolled Resource Consumption

Improper Resource Shutdown or Release

Further reading

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Sample evidence handover

Server-Side Request Forgery in `webhooks/receiver`