CWE-584 Base Borrador

Return Inside Finally Block

This vulnerability occurs when a function places a return statement inside a finally block. This dangerous pattern silently discards any unhandled exceptions thrown earlier in the try block, making…

Definición

What is CWE-584?

This vulnerability occurs when a function places a return statement inside a finally block. This dangerous pattern silently discards any unhandled exceptions thrown earlier in the try block, making errors invisible and undermining application stability.
A finally block is designed to execute cleanup code regardless of whether an exception occurs in the try or catch blocks. However, if you place a return statement inside finally, it overrides the normal exception propagation. When an exception is thrown in the try block but not caught before finally executes, the return in the finally block takes precedence. The function then exits normally, returning a value and completely discarding the original exception, as if the error never happened. This creates a severe debugging and reliability issue because critical failure signals are lost. Developers are left with no stack trace, log entry, or indication that something went wrong, leading to silent data corruption, incorrect program states, and failures that are extremely difficult to diagnose. To avoid this, ensure return statements are placed in try or catch blocks, not in finally, and handle resource cleanup without altering the control flow for exceptions.
Impacto en el mundo real

Real-world CVEs caused by CWE-584

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

    Identifica una ruta de código que maneje entrada no confiable sin validación.

  2. 2

    Crea un payload que ejercite el comportamiento inseguro — inyección, traversal, overflow o abuso de lógica.

  3. 3

    Envía el payload a través de una solicitud normal y observa la reacción de la aplicación.

  4. 4

    Itera hasta que la respuesta filtre datos, ejecute código del atacante o escale privilegios.

Ejemplo de código vulnerable

Vulnerable Java

In the following code excerpt, the IllegalArgumentException will never be delivered to the caller. The finally block will cause the exception to be discarded.

Vulnerable Java 
try {
  	...
  	throw IllegalArgumentException();
  }
  finally {
  	return r;
  }
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-584

  • Implementation Do not use a return statement inside the finally block. The finally block should have "cleanup" code.
Señales de detección

How to detect CWE-584

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.)

Auto-corrección de Plexicus

Plexicus detecta automáticamente CWE-584 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-584?

This vulnerability occurs when a function places a return statement inside a finally block. This dangerous pattern silently discards any unhandled exceptions thrown earlier in the try block, making errors invisible and undermining application stability.

¿Qué gravedad tiene CWE-584?

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-584?

MITRE no ha especificado plataformas afectadas para esta CWE — puede aplicar a la mayoría de los stacks de aplicaciones.

¿Cómo puedo prevenir CWE-584?

Do not use a return statement inside the finally block. The finally block should have "cleanup" code.

¿Cómo detecta y corrige Plexicus CWE-584?

El motor SAST de Plexicus detecta la firma de flujo de datos para CWE-584 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-584?

MITRE publica la definición canónica en https://cwe.mitre.org/data/definitions/584.html. También puedes consultar la documentación de OWASP y NIST para guías relacionadas.

Debilidades relacionadas

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Recursos

Further reading

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