CWE-691 Pilar Borrador

Insufficient Control Flow Management

This vulnerability occurs when a program's execution flow isn't properly managed, allowing attackers to bypass critical checks, trigger unexpected code paths, or disrupt normal operation.

Definición

What is CWE-691?

This vulnerability occurs when a program's execution flow isn't properly managed, allowing attackers to bypass critical checks, trigger unexpected code paths, or disrupt normal operation.
Insufficient control flow management happens when developers don't anticipate all possible execution states or fail to implement proper validation at decision points. This can include missing break statements in switch cases, poorly constructed loops that can be prematurely exited, or inadequate validation that allows attackers to skip over security checks. Without clear guardrails, the program's logic can be manipulated to reach code sections under unauthorized conditions. To prevent this, developers should implement strict state management and validate every transition in the program's logic flow. Use defensive programming techniques like complete condition coverage, explicit state machines, and mandatory checks before critical operations. Always assume that attackers will try to find unexpected paths through your code, and design your control flow to be resilient against such manipulation.
Impacto en el mundo real

Real-world CVEs caused by CWE-691

  • 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-2014-1266

    chain: incorrect "goto" in Apple SSL product bypasses certificate validation, allowing Adversary-in-the-Middle (AITM) attack (Apple "goto fail" bug). CWE-705 (Incorrect Control Flow Scoping) -> CWE-561 (Dead Code) -> CWE-295 (Improper Certificate Validation) -> CWE-393 (Return of Wrong Status Code) -> CWE-300 (Channel Accessible by Non-Endpoint).

  • CVE-2011-1027

    Chain: off-by-one error (CWE-193) leads to infinite loop (CWE-835) using invalid hex-encoded characters.

Cómo lo explotan los atacantes

Ruta del atacante paso a paso

  1. 1

    The following function attempts to acquire a lock in order to perform operations on a shared resource.

  2. 2

    However, the code does not check the value returned by pthread_mutex_lock() for errors. If pthread_mutex_lock() cannot acquire the mutex for any reason, the function may introduce a race condition into the program and result in undefined behavior.

  3. 3

    In order to avoid data races, correctly written programs must check the result of thread synchronization functions and appropriately handle all errors, either by attempting to recover from them or reporting them to higher levels.

  4. 4

    In this example, the programmer has indented the statements to call Do_X() and Do_Y(), as if the intention is that these functions are only called when the condition is true. However, because there are no braces to signify the block, Do_Y() will always be executed, even if the condition is false.

  5. 5

    This might not be what the programmer intended. When the condition is critical for security, such as in making a security decision or detecting a critical error, this may produce a vulnerability.

Ejemplo de código vulnerable

Vulnerable C

The following function attempts to acquire a lock in order to perform operations on a shared resource.

Vulnerable C 
void f(pthread_mutex_t *mutex) {
  		pthread_mutex_lock(mutex);
```
/* access shared resource */* 
  		
  		
  		pthread_mutex_unlock(mutex);}
Ejemplo de código seguro

Secure C

In order to avoid data races, correctly written programs must check the result of thread synchronization functions and appropriately handle all errors, either by attempting to recover from them or reporting them to higher levels.

Seguro C 
int f(pthread_mutex_t *mutex) {
  		int result;
  		result = pthread_mutex_lock(mutex);
  		if (0 != result)
  			return result;
```
/* access shared resource */* 
  		
  		
  		return pthread_mutex_unlock(mutex);}
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-691

  • 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-691

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-691 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-691?

This vulnerability occurs when a program's execution flow isn't properly managed, allowing attackers to bypass critical checks, trigger unexpected code paths, or disrupt normal operation.

¿Qué gravedad tiene CWE-691?

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-691?

MITRE lists the following affected platforms: Not Technology-Specific.

¿Cómo puedo prevenir CWE-691?

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-691?

El motor SAST de Plexicus detecta la firma de flujo de datos para CWE-691 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-691?

MITRE publica la definición canónica en https://cwe.mitre.org/data/definitions/691.html. También puedes consultar la documentación de OWASP y NIST para guías relacionadas.

Debilidades relacionadas

Weaknesses related to CWE-691

CWE-1265 Hijo

Unintended Reentrant Invocation of Non-reentrant Code Via Nested Calls

This vulnerability occurs when a non-reentrant function is called, and during its execution, another call is triggered that unexpectedly…

CWE-1281 Hijo

Sequence of Processor Instructions Leads to Unexpected Behavior

Certain sequences of valid and invalid processor instructions can cause the CPU to lock up or behave unpredictably, often requiring a hard…

CWE-362 Hijo

Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')

A race condition occurs when multiple processes or threads access a shared resource simultaneously without proper coordination, creating a…

CWE-430 Hijo

Deployment of Wrong Handler

This vulnerability occurs when a system incorrectly assigns or routes an object to the wrong processing component.

CWE-431 Hijo

Missing Handler

This vulnerability occurs when a software component lacks the necessary code to properly handle an error or unexpected event.

CWE-662 Hijo

Improper Synchronization

This vulnerability occurs when a multi-threaded or multi-process application allows shared resources to be accessed by multiple threads or…

CWE-670 Hijo

Always-Incorrect Control Flow Implementation

This weakness occurs when a section of code is structured in a way that always executes incorrectly, regardless of input or conditions.…

CWE-696 Hijo

Incorrect Behavior Order

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

CWE-705 Hijo

Incorrect Control Flow Scoping

This vulnerability occurs when a program fails to return execution to the correct point in the code after finishing a specific operation…

Recursos

Further reading

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