CWE-609 Base Borrador

Double-Checked Locking

Double-checked locking is an insufficient synchronization pattern where a program checks a resource's state, acquires a lock, and checks the state again before initialization, failing to guarantee…

Definición

What is CWE-609?

Double-checked locking is an insufficient synchronization pattern where a program checks a resource's state, acquires a lock, and checks the state again before initialization, failing to guarantee thread safety across all systems.
Double-checked locking attempts to optimize performance by avoiding the cost of synchronization on every access. A thread first checks if a resource (like an object) is initialized without a lock. If it appears uninitialized, the thread then acquires a lock, performs a second check, and only initializes the resource if the second check also confirms it's needed. This pattern aims to minimize lock contention but is fundamentally flawed. The core issue is that this sequence is not guaranteed to be atomic or visible in the same order to other threads running concurrently. Without proper synchronization on the initial check, other threads might see a partially constructed object or cache the uninitialized state, leading to unpredictable behavior and crashes. Because memory model guarantees vary across programming languages and hardware architectures, this pattern is unreliable and should be replaced with thread-safe initialization methods.
Impacto en el mundo real

Real-world CVEs caused by CWE-609

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

    It may seem that the following bit of code achieves thread safety while avoiding unnecessary synchronization...

  2. 2

    The programmer wants to guarantee that only one Helper() object is ever allocated, but does not want to pay the cost of synchronization every time this code is called.

  3. 3

    Suppose that helper is not initialized. Then, thread A sees that helper==null and enters the synchronized block and begins to execute:

  4. 4

    If a second thread, thread B, takes over in the middle of this call and helper has not finished running the constructor, then thread B may make calls on helper while its fields hold incorrect values.

Ejemplo de código vulnerable

Vulnerable Java

It may seem that the following bit of code achieves thread safety while avoiding unnecessary synchronization...

Vulnerable Java 
if (helper == null) {
  		synchronized (this) {
  			if (helper == null) {
  				helper = new Helper();
  			}
  		}
  }
  return helper;
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-609

  • Implementation While double-checked locking can be achieved in some languages, it is inherently flawed in Java before 1.5, and cannot be achieved without compromising platform independence. Before Java 1.5, only use of the synchronized keyword is known to work. Beginning in Java 1.5, use of the "volatile" keyword allows double-checked locking to work successfully, although there is some debate as to whether it achieves sufficient performance gains. See references.
Señales de detección

How to detect CWE-609

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-609 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.

Solicitar demo Probar Plexicus gratis
Preguntas frecuentes

Frequently asked questions

¿Qué es CWE-609?

Double-checked locking is an insufficient synchronization pattern where a program checks a resource's state, acquires a lock, and checks the state again before initialization, failing to guarantee thread safety across all systems.

¿Qué gravedad tiene CWE-609?

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-609?

MITRE lists the following affected platforms: Java.

¿Cómo puedo prevenir CWE-609?

While double-checked locking can be achieved in some languages, it is inherently flawed in Java before 1.5, and cannot be achieved without compromising platform independence. Before Java 1.5, only use of the synchronized keyword is known to work. Beginning in Java 1.5, use of the "volatile" keyword allows double-checked locking to work successfully, although there is some debate as to whether it achieves sufficient performance gains. See references.

¿Cómo detecta y corrige Plexicus CWE-609?

El motor SAST de Plexicus detecta la firma de flujo de datos para CWE-609 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-609?

MITRE publica la definición canónica en https://cwe.mitre.org/data/definitions/609.html. También puedes consultar la documentación de OWASP y NIST para guías relacionadas.

Debilidades relacionadas

Weaknesses related to CWE-609

CWE-667 Padre

Improper Locking

This vulnerability occurs when a program fails to correctly acquire or release a lock on a shared resource, such as a file, database…

CWE-1232 Hermano

Improper Lock Behavior After Power State Transition

This vulnerability occurs when a hardware lock bit, designed to protect critical system configuration registers, is improperly reset or…

CWE-1233 Hermano

Security-Sensitive Hardware Controls with Missing Lock Bit Protection

This vulnerability occurs when a hardware device uses a lock bit to protect critical configuration registers, but the lock fails to…

CWE-1234 Hermano

Hardware Internal or Debug Modes Allow Override of Locks

Hardware debug modes or internal states can bypass critical system lock protections, allowing unauthorized changes to device configuration.

CWE-412 Hermano

Unrestricted Externally Accessible Lock

This vulnerability occurs when a system correctly checks for a lock's existence, but an unauthorized external actor can control or…

CWE-413 Hermano

Improper Resource Locking

This vulnerability occurs when an application fails to properly lock a shared resource, such as a file or memory location, before…

CWE-414 Hermano

Missing Lock Check

This vulnerability occurs when software fails to verify that a proper synchronization lock is active before accessing or modifying a…

CWE-764 Hermano

Multiple Locks of a Critical Resource

This vulnerability occurs when a critical resource, such as a file, data structure, or connection, is locked more times than the software…

CWE-765 Hermano

Multiple Unlocks of a Critical Resource

This vulnerability occurs when a critical resource, like a lock or semaphore, is unlocked more times than it was locked, putting the…

Recursos

Further reading

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.

Comenzar gratis Reservar una demo