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-492 Variante Borrador
Use of Inner Class Containing Sensitive Data
Using inner classes to handle sensitive data can unintentionally expose that data because of how Java compiles them. The compiler transforms inner classes into separate, package-visible classes,…
Definición
What is CWE-492?
Using inner classes to handle sensitive data can unintentionally expose that data because of how Java compiles them. The compiler transforms inner classes into separate, package-visible classes, which can bypass the intended private access restrictions.
Inner classes in Java create hidden security risks due to their compilation process. While your source code might declare an inner class as private to its enclosing class, the Java bytecode has no built-in support for this relationship. To make it work, the compiler converts the inner class into a separate peer class with package-level access. This means code you intended to keep private within a single class becomes accessible to all other classes in the same package.
This becomes especially dangerous because inner classes can access private fields of their outer class. To allow this access in the transformed bytecode, the compiler silently changes those private fields to protected scope. As a result, sensitive data you marked as private can be exposed through the newly created peer class, breaking your intended encapsulation and creating a potential data leak.
Impacto en el mundo real
Real-world CVEs caused by CWE-492
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
The following Java Applet code mistakenly makes use of an inner class.
- 2
The following example shows a basic use of inner classes. The class OuterClass contains the private member inner class InnerClass. The private inner class InnerClass includes the method concat that accesses the private member variables of the class OuterClass to output the value of one of the private member variables of the class OuterClass and returns a string that is a concatenation of one of the private member variables of the class OuterClass, the separator input parameter of the method and the private member variable of the class InnerClass.
- 3
Although this is an acceptable use of inner classes it demonstrates one of the weaknesses of inner classes that inner classes have complete access to all member variables and methods of the enclosing class even those that are declared private and protected. When inner classes are compiled and translated into Java bytecode the JVM treats the inner class as a peer class with package level access to the enclosing class.
- 4
To avoid this weakness of inner classes, consider using either static inner classes, local inner classes, or anonymous inner classes.
- 5
The following Java example demonstrates the use of static inner classes using the previous example. The inner class InnerClass is declared using the static modifier that signifies that InnerClass is a static member of the enclosing class OuterClass. By declaring an inner class as a static member of the enclosing class, the inner class can only access other static members and methods of the enclosing class and prevents the inner class from accessing nonstatic member variables and methods of the enclosing class. In this case the inner class InnerClass can only access the static member variable memberTwo of the enclosing class OuterClass but cannot access the nonstatic member variable memberOne.
Ejemplo de código vulnerable
Vulnerable Java
The following Java Applet code mistakenly makes use of an inner class.
public final class urlTool extends Applet {
private final class urlHelper {
...
}
...
} Ejemplo de código seguro
Secure Java
The following Java example demonstrates the use of static inner classes using the previous example. The inner class InnerClass is declared using the static modifier that signifies that InnerClass is a static member of the enclosing class OuterClass. By declaring an inner class as a static member of the enclosing class, the inner class can only access other static members and methods of the enclosing class and prevents the inner class from accessing nonstatic member variables and methods of the enclosing class. In this case the inner class InnerClass can only access the static member variable memberTwo of the enclosing class OuterClass but cannot access the nonstatic member variable memberOne.
public class OuterClass {
```
// private member variables of OuterClass*
private String memberOne;
private static String memberTwo;
*// constructor of OuterClass*
public OuterClass(String varOne, String varTwo) {
```
this.memberOne = varOne;
this.memberTwo = varTwo;
}
```
// InnerClass is a static inner class of OuterClass*
private static class InnerClass {
```
private String innerMemberOne;
public InnerClass(String innerVarOne) {
this.innerMemberOne = innerVarOne;
}
public String concat(String separator) {
```
// InnerClass only has access to static member variables of OuterClass*
return memberTwo + separator + this.innerMemberOne;}}} 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-492
- Implementation Using sealed classes protects object-oriented encapsulation paradigms and therefore protects code from being extended in unforeseen ways.
- Implementation Inner Classes do not provide security. Warning: Never reduce the security of the object from an outer class, going to an inner class. If an outer class is final or private, ensure that its inner class is private as well.
Señales de detección
How to detect CWE-492
Plexicus detecta automáticamente CWE-492 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.
Preguntas frecuentes ¿Qué es CWE-492?
¿Qué gravedad tiene CWE-492?
¿Qué lenguajes o plataformas se ven afectados por CWE-492?
¿Cómo puedo prevenir CWE-492?
¿Cómo detecta y corrige Plexicus CWE-492?
¿Dónde puedo aprender más sobre CWE-492?
Frequently asked questions
¿Qué es CWE-492?
Using inner classes to handle sensitive data can unintentionally expose that data because of how Java compiles them. The compiler transforms inner classes into separate, package-visible classes, which can bypass the intended private access restrictions.
¿Qué gravedad tiene CWE-492?
MITRE califica la probabilidad de explotación como Media — la explotación es realista pero suele requerir condiciones específicas.
¿Qué lenguajes o plataformas se ven afectados por CWE-492?
MITRE lists the following affected platforms: Java.
¿Cómo puedo prevenir CWE-492?
Using sealed classes protects object-oriented encapsulation paradigms and therefore protects code from being extended in unforeseen ways. Inner Classes do not provide security. Warning: Never reduce the security of the object from an outer class, going to an inner class. If an outer class is final or private, ensure that its inner class is private as well.
¿Cómo detecta y corrige Plexicus CWE-492?
El motor SAST de Plexicus detecta la firma de flujo de datos para CWE-492 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-492?
MITRE publica la definición canónica en https://cwe.mitre.org/data/definitions/492.html. También puedes consultar la documentación de OWASP y NIST para guías relacionadas.
Debilidades relacionadas
Weaknesses related to CWE-492
CWE-668 Padre
Exposure of Resource to Wrong Sphere
This vulnerability occurs when an application unintentionally makes a resource accessible to users or systems that should not have…
CWE-1189 Hermano
Improper Isolation of Shared Resources on System-on-a-Chip (SoC)
This vulnerability occurs when a System-on-a-Chip (SoC) fails to properly separate shared hardware resources between secure (trusted) and…
CWE-1282 Hermano
Assumed-Immutable Data is Stored in Writable Memory
This vulnerability occurs when data that should be permanent and unchangeable—like a bootloader, device IDs, or one-time configuration…
CWE-1327 Hermano
Binding to an Unrestricted IP Address
This vulnerability occurs when software or a service is configured to bind to the IP address 0.0.0.0 (or :: in IPv6), which acts as a…
CWE-1331 Hermano
Improper Isolation of Shared Resources in Network On Chip (NoC)
This vulnerability occurs when a Network on Chip (NoC) fails to properly separate its internal, shared resources—like buffers, switches,…
CWE-134 Hermano
Use of Externally-Controlled Format String
This vulnerability occurs when a program uses a format string from an untrusted, external source (like user input, a network packet, or a…
CWE-200 Hermano
Exposure of Sensitive Information to an Unauthorized Actor
This weakness occurs when an application unintentionally reveals sensitive data to someone who shouldn't have access to it.
CWE-374 Hermano
Passing Mutable Objects to an Untrusted Method
This vulnerability occurs when a function receives a direct reference to mutable data, such as an object or array, instead of a safe copy…
CWE-375 Hermano
Returning a Mutable Object to an Untrusted Caller
This vulnerability occurs when a method directly returns a reference to its internal mutable data, allowing untrusted calling code to…
Recursos
Further reading
- MITRE — CWE-492 oficial https://cwe.mitre.org/data/definitions/492.html
- Seven Pernicious Kingdoms: A Taxonomy of Software Security Errors https://samate.nist.gov/SSATTM_Content/papers/Seven%20Pernicious%20Kingdoms%20-%20Taxonomy%20of%20Sw%20Security%20Errors%20-%20Tsipenyuk%20-%20Chess%20-%20McGraw.pdf
Listo cuando tú lo estés
Deja de pagar por desarrollador.
Empieza a cerrar el bucle.
Plexicus es el ASPM nativo de IA que escanea, filtra, corrige, pentestea y explica — de forma autónoma. Desarrolladores ilimitados, repos ilimitados, acciones de IA de uso justo. Nivel gratuito real, €269/mo anual cuando estés listo.