CWE-767 Base Incompleto

Access to Critical Private Variable via Public Method

This vulnerability occurs when a class exposes a public method that directly accesses or alters a private variable.

Definición

What is CWE-767?

This vulnerability occurs when a class exposes a public method that directly accesses or alters a private variable.
Exposing a private variable through a public method breaks a core principle of encapsulation. It allows external code, including potential attacker-controlled inputs, to bypass intended controls and directly manipulate sensitive internal data. This can lead to the variable holding values the rest of the codebase never expects, corrupting the application's state and violating critical security assumptions. Beyond unexpected modification, this flaw can also lead to information disclosure. An attacker might use the public method to read the private variable's contents, potentially leaking sensitive data like internal flags, cryptographic keys, or user information. This exposed data not only compromises confidentiality but can also provide attackers with the insights needed to craft more sophisticated and targeted follow-up attacks.
Impacto en el mundo real

Real-world CVEs caused by CWE-767

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

    The following example declares a critical variable to be private, and then allows the variable to be modified by public methods.

  2. 2

    The following example could be used to implement a user forum where a single user (UID) can switch between multiple profiles (PID).

  3. 3

    The programmer implemented setPID with the intention of modifying the PID variable, but due to a typo. accidentally specified the critical variable UID instead. If the program allows profile IDs to be between 1 and 10, but a UID of 1 means the user is treated as an admin, then a user could gain administrative privileges as a result of this typo.

Ejemplo de código vulnerable

Vulnerable C++

The following example declares a critical variable to be private, and then allows the variable to be modified by public methods.

Vulnerable C++ 
private: float price;
  public: void changePrice(float newPrice) {
  	price = newPrice;
  }
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-767

  • Implementation Use class accessor and mutator methods appropriately. Perform validation when accepting data from a public method that is intended to modify a critical private variable. Also be sure that appropriate access controls are being applied when a public method interfaces with critical data.
Señales de detección

How to detect CWE-767

SAST High

Ejecuta análisis estático (SAST) sobre el código buscando el patrón inseguro en el flujo de datos.

DAST Moderate

Ejecuta pruebas dinámicas de seguridad de aplicaciones (DAST) contra el endpoint en vivo.

Runtime Moderate

Vigila los logs en tiempo de ejecución para detectar trazas de excepción inusuales, entradas malformadas o intentos de bypass de autorización.

Code review Moderate

Revisión de código: marca cualquier código nuevo que maneje entrada desde esta superficie sin usar los helpers validados del framework.

Auto-corrección de Plexicus

Plexicus detecta automáticamente CWE-767 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-767?

This vulnerability occurs when a class exposes a public method that directly accesses or alters a private variable.

¿Qué gravedad tiene CWE-767?

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-767?

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

¿Cómo puedo prevenir CWE-767?

Use class accessor and mutator methods appropriately. Perform validation when accepting data from a public method that is intended to modify a critical private variable. Also be sure that appropriate access controls are being applied when a public method interfaces with critical data.

¿Cómo detecta y corrige Plexicus CWE-767?

El motor SAST de Plexicus detecta la firma de flujo de datos para CWE-767 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-767?

MITRE publica la definición canónica en https://cwe.mitre.org/data/definitions/767.html. También puedes consultar la documentación de OWASP y NIST para guías relacionadas.

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Recursos

Further reading

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