CWE-696 Clase Incompleto

Incorrect Behavior Order

This weakness occurs when a system executes multiple dependent actions in the wrong sequence, leading to unexpected and potentially vulnerable states.

Definición

What is CWE-696?

This weakness occurs when a system executes multiple dependent actions in the wrong sequence, leading to unexpected and potentially vulnerable states.
Think of this as a race condition in logic, not just in threads. When operations like initialization, validation, state updates, or cleanup happen out of order, the application can be left in an inconsistent state. For example, using a resource before it's properly initialized, checking permissions after granting access, or cleaning up a log file before writing an error entry can all open doors to security issues, crashes, or data corruption. Developers can prevent this by explicitly modeling and enforcing the required sequence of operations in their code. Using state machines, well-defined lifecycle hooks, or design patterns that mandate order (like dependency injection or builder patterns) can help. Always ask: 'What must happen before this step, and what depends on this step being complete?' Testing should include verifying behavior sequences under different conditions, not just individual function outputs.
Impacto en el mundo real

Real-world CVEs caused by CWE-696

  • CVE-2019-9805

    Chain: Creation of the packet client occurs before initialization is complete (CWE-696) resulting in a read from uninitialized memory (CWE-908), causing memory corruption.

  • CVE-2007-5191

    file-system management programs call the setuid and setgid functions in the wrong order and do not check the return values, allowing attackers to gain unintended privileges

  • CVE-2007-1588

    C++ web server program calls Process::setuid before calling Process::setgid, preventing it from dropping privileges, potentially allowing CGI programs to be called with higher privileges than intended

  • CVE-2022-37734

    Chain: lexer in Java-based GraphQL server does not enforce maximum of tokens early enough (CWE-696), allowing excessive CPU consumption (CWE-1176)

Cómo lo explotan los atacantes

Ruta del atacante paso a paso

  1. 1

    The following code attempts to validate a given input path by checking it against an allowlist and then return the canonical path. In this specific case, the path is considered valid if it starts with the string "/safe_dir/".

  2. 2

    The problem with the above code is that the validation step occurs before canonicalization occurs. An attacker could provide an input path of "/safe_dir/../" that would pass the validation step. However, the canonicalization process sees the double dot as a traversal to the parent directory and hence when canonicized the path would become just "/".

  3. 3

    To avoid this problem, validation should occur after canonicalization takes place. In this case canonicalization occurs during the initialization of the File object. The code below fixes the issue.

  4. 4

    This function prints the contents of a specified file requested by a user.

  5. 5

    This code first reads a specified file into memory, then prints the file if the user is authorized to see its contents. The read of the file into memory may be resource intensive and is unnecessary if the user is not allowed to see the file anyway.

Ejemplo de código vulnerable

Vulnerable Java

The following code attempts to validate a given input path by checking it against an allowlist and then return the canonical path. In this specific case, the path is considered valid if it starts with the string "/safe_dir/".

Vulnerable Java 
String path = getInputPath();
  if (path.startsWith("/safe_dir/"))
  {
  	File f = new File(path);
  	return f.getCanonicalPath();
  }
Ejemplo de código seguro

Secure Java

To avoid this problem, validation should occur after canonicalization takes place. In this case canonicalization occurs during the initialization of the File object. The code below fixes the issue.

Seguro Java 
String path = getInputPath();
  File f = new File(path);
  if (f.getCanonicalPath().startsWith("/safe_dir/"))
  {
  	return f.getCanonicalPath();
  }
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-696

  • Architecture Use safe-by-default frameworks and APIs that prevent the unsafe pattern from being expressible.
  • Implementation Validate input at trust boundaries; use allowlists, not denylists.
  • Implementation Apply the principle of least privilege to credentials, file paths, and runtime permissions.
  • Testing Cover this weakness in CI: SAST rules + targeted unit tests for the data flow.
  • Operation Monitor logs for the runtime signals listed in the next section.
Señales de detección

How to detect CWE-696

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-696 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-696?

This weakness occurs when a system executes multiple dependent actions in the wrong sequence, leading to unexpected and potentially vulnerable states.

¿Qué gravedad tiene CWE-696?

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-696?

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

¿Cómo puedo prevenir CWE-696?

Use safe-by-default frameworks, validate untrusted input at trust boundaries, and apply the principle of least privilege. Cover the data-flow signature in CI with SAST.

¿Cómo detecta y corrige Plexicus CWE-696?

El motor SAST de Plexicus detecta la firma de flujo de datos para CWE-696 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-696?

MITRE publica la definición canónica en https://cwe.mitre.org/data/definitions/696.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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