CWE-606 Base Borrador

Unchecked Input for Loop Condition

This vulnerability occurs when an application fails to properly validate or limit user-supplied values that control loop iterations. Without these checks, malicious input can force the program into…

Definición

What is CWE-606?

This vulnerability occurs when an application fails to properly validate or limit user-supplied values that control loop iterations. Without these checks, malicious input can force the program into an endless or excessively long loop, consuming system resources and leading to denial of service or application instability.
At its core, this weakness allows an attacker to manipulate a program's flow by controlling how many times a loop executes. Common scenarios include using an unexpectedly large integer for a counter, a negative number that bypasses termination logic, or a specially crafted string that causes unexpected parsing behavior within the loop condition. Developers often trust these values from sources like configuration files, APIs, or user inputs without implementing strict bounds checking. To prevent this, always validate and sanitize any external input before it determines loop behavior. Implement explicit limits on maximum iterations, use signed/unsigned integer checks to prevent wrap-around issues, and consider adding timeout mechanisms for processing loops. Treat loop control variables with the same level of distrust as any other user input, as they directly control resource consumption and application availability.
Impacto en el mundo real

Real-world CVEs caused by CWE-606

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

    The following example demonstrates the weakness.

  2. 2

    In the following C/C++ example the method processMessageFromSocket() will get a message from a socket, placed into a buffer, and will parse the contents of the buffer into a structure that contains the message length and the message body. A for loop is used to copy the message body into a local character string which will be passed to another method for processing.

  3. 3

    However, the message length variable (msgLength) from the structure is used as the condition for ending the for loop without validating that msgLength accurately reflects the actual length of the message body (CWE-606). If msgLength indicates a length that is longer than the size of a message body (CWE-130), then this can result in a buffer over-read by reading past the end of the buffer (CWE-126).

Ejemplo de código vulnerable

Vulnerable C

The following example demonstrates the weakness.

Vulnerable C 
void iterate(int n){
  	int i;
  	for (i = 0; i < n; i++){
  		foo();
  	}
  }
  void iterateFoo()
  {
  	unsigned int num;
  	scanf("%u",&num);
  	iterate(num);
  }
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-606

  • Implementation Do not use user-controlled data for loop conditions.
  • Implementation Perform input validation.
Señales de detección

How to detect CWE-606

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-606 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-606?

This vulnerability occurs when an application fails to properly validate or limit user-supplied values that control loop iterations. Without these checks, malicious input can force the program into an endless or excessively long loop, consuming system resources and leading to denial of service or application instability.

¿Qué gravedad tiene CWE-606?

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-606?

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

¿Cómo puedo prevenir CWE-606?

Do not use user-controlled data for loop conditions. Perform input validation.

¿Cómo detecta y corrige Plexicus CWE-606?

El motor SAST de Plexicus detecta la firma de flujo de datos para CWE-606 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-606?

MITRE publica la definición canónica en https://cwe.mitre.org/data/definitions/606.html. También puedes consultar la documentación de OWASP y NIST para guías relacionadas.

Debilidades relacionadas

Weaknesses related to CWE-606

CWE-1284 Padre

Improper Validation of Specified Quantity in Input

This vulnerability occurs when an application accepts user input meant to define a quantity—like a number, size, or count—but fails to…

CWE-834 Puede preceder

Excessive Iteration

This vulnerability occurs when a program runs a loop too many times because it lacks proper limits on its iterations.

Recursos

Further reading

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