CWE-495: Private Data Structure Returned From A Public Method

Definición

What is CWE-495?

This vulnerability occurs when a public method directly returns a reference to a private, internal data structure. Because the reference is live, external callers can bypass intended controls and modify the data unexpectedly, corrupting the application's state.

This flaw breaks a core principle of encapsulation in object-oriented design. The private data structure—like an array, collection, or object—is meant to be managed solely by the class's own methods. By handing out a direct reference, you allow external code to add, remove, or alter elements without validation, leading to data corruption, security bypasses, or crashes that are difficult to debug. The fix is to return either a copy of the data (defensive copying) or an immutable view, ensuring the internal state remains protected. Identifying every instance of this pattern across a large codebase can be tedious. While SAST tools can flag the risky return statements, Plexicus uses AI to analyze the context and automatically suggest the correct remediation—such as implementing `Collections.unmodifiableList()` in Java or a slice copy in Go—saving developers hours of manual refactoring and ensuring consistent fixes.

Impacto en el mundo real

Real-world CVEs caused by CWE-495

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

Here, a public method in a Java class returns a reference to a private array. Given that arrays in Java are mutable, any modifications made to the returned reference would be reflected in the original private array.

Vulnerable Java

private String[] colors;
  public String[] getColors() {
  	return colors;
  }

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-495

Implementation Declare the method private.
Implementation Clone the member data and keep an unmodified version of the data private to the object.
Implementation Use public setter methods that govern how a private member can be modified.

Señales de detección

How to detect CWE-495

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-495

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

Plexicus turns CWE catalogs into evidence: every CWE-pattern is matched against your real code graph, reach is proven on a sandbox clone, and verified findings ship as reviewed PRs.

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Preguntas frecuentes

Frequently asked questions

¿Qué es CWE-495?

This vulnerability occurs when a public method directly returns a reference to a private, internal data structure. Because the reference is live, external callers can bypass intended controls and modify the data unexpectedly, corrupting the application's state.

¿Qué gravedad tiene CWE-495?

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-495?

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

¿Cómo puedo prevenir CWE-495?

Declare the method private. Clone the member data and keep an unmodified version of the data private to the object.

¿Cómo detecta y corrige Plexicus CWE-495?

El motor SAST de Plexicus detecta la firma de flujo de datos para CWE-495 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-495?

MITRE publica la definición canónica en https://cwe.mitre.org/data/definitions/495.html. También puedes consultar la documentación de OWASP y NIST para guías relacionadas.

Debilidades relacionadas

Weaknesses related to CWE-495

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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Private Data Structure Returned From A Public Method

What is CWE-495?

Real-world CVEs caused by CWE-495

Ruta del atacante paso a paso

Vulnerable Java

Secure pseudo

How to prevent CWE-495

How to detect CWE-495

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

Frequently asked questions

Weaknesses related to CWE-495

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`