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-766 Base Incompleto
Critical Data Element Declared Public
This vulnerability occurs when a critical piece of data—like a variable, field, or class member—is mistakenly declared as public when it should be kept private according to the application's…
Definición
What is CWE-766?
This vulnerability occurs when a critical piece of data—like a variable, field, or class member—is mistakenly declared as public when it should be kept private according to the application's security design.
Declaring sensitive data as public breaks fundamental security principles like encapsulation and least privilege. It directly exposes critical information, such as internal state, configuration secrets, or authentication tokens, to any other part of the codebase or, in some languages and contexts, to external actors. This creates a clear and immediate attack surface, making it trivial for an attacker to read or modify data that should be strictly controlled.
Beyond the direct security flaw, this practice severely damages code maintainability and security hygiene. It becomes difficult to track how and where this critical data is being used or altered, scattering logic that should be centralized. This "spaghetti code" effect makes identifying the root cause of bugs or vulnerabilities more time-consuming and increases the risk of introducing new security weaknesses during future development or refactoring.
Impacto en el mundo real
Real-world CVEs caused by CWE-766
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variables declared public allow remote read of system properties such as user name and home directory.
Cómo lo explotan los atacantes
Ruta del atacante paso a paso
- 1
The following example declares a critical variable public, making it accessible to anyone with access to the object in which it is contained.
- 2
Instead, the critical data should be declared private.
- 3
Even though this example declares the password to be private, there are other possible issues with this implementation, such as the possibility of recovering the password from process memory (CWE-257).
- 4
The following example shows a basic user account class that includes member variables for the username and password as well as a public constructor for the class and a public method to authorize access to the user account.
- 5
However, the member variables username and password are declared public and therefore will allow access and changes to the member variables to anyone with access to the object. These member variables should be declared private as shown below to prevent unauthorized access and changes.
Ejemplo de código vulnerable
Vulnerable C++
The following example declares a critical variable public, making it accessible to anyone with access to the object in which it is contained.
public: char* password; Ejemplo de código seguro
Secure C++
Instead, the critical data should be declared private.
private: char* password; 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-766
- Implementation Data should be private, static, and final whenever possible. This will assure that your code is protected by instantiating early, preventing access, and preventing tampering.
Señales de detección
How to detect CWE-766
CWE-766
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.
Preguntas frecuentes ¿Qué es CWE-766?
¿Qué gravedad tiene CWE-766?
¿Qué lenguajes o plataformas se ven afectados por CWE-766?
¿Cómo puedo prevenir CWE-766?
¿Cómo detecta y corrige Plexicus CWE-766?
¿Dónde puedo aprender más sobre CWE-766?
Frequently asked questions
¿Qué es CWE-766?
This vulnerability occurs when a critical piece of data—like a variable, field, or class member—is mistakenly declared as public when it should be kept private according to the application's security design.
¿Qué gravedad tiene CWE-766?
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-766?
MITRE lists the following affected platforms: C++, C#, Java.
¿Cómo puedo prevenir CWE-766?
Data should be private, static, and final whenever possible. This will assure that your code is protected by instantiating early, preventing access, and preventing tampering.
¿Cómo detecta y corrige Plexicus CWE-766?
El motor SAST de Plexicus detecta la firma de flujo de datos para CWE-766 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-766?
MITRE publica la definición canónica en https://cwe.mitre.org/data/definitions/766.html. También puedes consultar la documentación de OWASP y NIST para guías relacionadas.
Debilidades relacionadas
Weaknesses related to CWE-766
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Insecure Inherited Permissions
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CWE-279 Hermano
Incorrect Execution-Assigned Permissions
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Improper Preservation of Permissions
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¿Listo para validar lo que importa?
Listo para validar lo que importa.
Plexicus es Proof-Driven AppSec: hallazgos validados, comprensión contextual y remediación revisada — anclada en evidencia, acotada contigo.