CWE-561 Base Borrador

Dead Code

Dead code refers to sections of a program that can never run during normal execution, effectively making them inactive and unreachable.

Definición

What is CWE-561?

Dead code refers to sections of a program that can never run during normal execution, effectively making them inactive and unreachable.
Dead code occurs when logic within the program, such as conditional statements or function calls, permanently prevents its execution. This often results from overly restrictive conditions, code that's been commented out but left in place, or legacy functions that are no longer invoked after software updates. While not directly exploitable like a vulnerability, it bloats the codebase, obscures real issues during security reviews, and can mislead developers about the program's actual behavior. From a security and maintenance perspective, dead code creates unnecessary noise during static analysis and manual audits, potentially causing real vulnerabilities to be overlooked. It also increases the attack surface by adding complexity without providing value. Regularly removing dead code through refactoring and using code coverage tools helps keep the application lean, understandable, and easier to secure.
Impacto en el mundo real

Real-world CVEs caused by CWE-561

  • 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).

Cómo lo explotan los atacantes

Ruta del atacante paso a paso

  1. 1

    The condition for the second if statement is impossible to satisfy. It requires that the variables be non-null. However, on the only path where s can be assigned a non-null value, there is a return statement.

  2. 2

    In the following class, two private methods call each other, but since neither one is ever invoked from anywhere else, they are both dead code.

  3. 3

    (In this case it is a good thing that the methods are dead: invoking either one would cause an infinite loop.)

  4. 4

    The field named glue is not used in the following class. The author of the class has accidentally put quotes around the field name, transforming it into a string constant.

Ejemplo de código vulnerable

Vulnerable C++

The condition for the second if statement is impossible to satisfy. It requires that the variables be non-null. However, on the only path where s can be assigned a non-null value, there is a return statement.

Vulnerable C++ 
String s = null;
  if (b) {
  	s = "Yes";
  	return;
  }
  if (s != null) {
  	Dead();
  }
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-561

  • Implementation Remove dead code before deploying the application.
  • Testing Use a static analysis tool to spot dead code.
Señales de detección

How to detect CWE-561

Architecture or Design Review High

According to SOAR [REF-1479], the following detection techniques may be useful: ``` Highly cost effective: ``` Inspection (IEEE 1028 standard) (can apply to requirements, design, source code, etc.) Formal Methods / Correct-By-Construction ``` Cost effective for partial coverage: ``` Attack Modeling

Automated Static Analysis - Binary or Bytecode High

According to SOAR [REF-1479], the following detection techniques may be useful: ``` Highly cost effective: ``` Binary / Bytecode Quality Analysis Compare binary / bytecode to application permission manifest

Dynamic Analysis with Manual Results Interpretation SOAR Partial

According to SOAR [REF-1479], the following detection techniques may be useful: ``` Cost effective for partial coverage: ``` Automated Monitored Execution

Automated Static Analysis SOAR Partial

According to SOAR [REF-1479], the following detection techniques may be useful: ``` Cost effective for partial coverage: ``` Permission Manifest Analysis

Automated Static Analysis - Source Code High

According to SOAR [REF-1479], the following detection techniques may be useful: ``` Highly cost effective: ``` Source Code Quality Analyzer ``` Cost effective for partial coverage: ``` Warning Flags Source code Weakness Analyzer Context-configured Source Code Weakness Analyzer

Dynamic Analysis with Automated Results Interpretation SOAR Partial

According to SOAR [REF-1479], the following detection techniques may be useful: ``` Cost effective for partial coverage: ``` Web Application Scanner Web Services Scanner Database Scanners

Auto-corrección de Plexicus

Plexicus detecta automáticamente CWE-561 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-561?

Dead code refers to sections of a program that can never run during normal execution, effectively making them inactive and unreachable.

¿Qué gravedad tiene CWE-561?

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-561?

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

¿Cómo puedo prevenir CWE-561?

Remove dead code before deploying the application. Use a static analysis tool to spot dead code.

¿Cómo detecta y corrige Plexicus CWE-561?

El motor SAST de Plexicus detecta la firma de flujo de datos para CWE-561 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-561?

MITRE publica la definición canónica en https://cwe.mitre.org/data/definitions/561.html. También puedes consultar la documentación de OWASP y NIST para guías relacionadas.

Debilidades relacionadas

Weaknesses related to CWE-561

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CWE-1071 Hermano

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CWE-110 Hermano

Struts: Validator Without Form Field

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CWE-563 Hermano

Assignment to Variable without Use

This vulnerability occurs when a value is stored in a variable, but that variable is never read or used in subsequent code, creating a…

Recursos

Further reading

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