CWE-755 Clase Incompleto Medium likelihood

Improper Handling of Exceptional Conditions

This vulnerability occurs when software fails to properly manage unexpected situations or errors, leaving it in an unstable or insecure state.

Definición

What is CWE-755?

This vulnerability occurs when software fails to properly manage unexpected situations or errors, leaving it in an unstable or insecure state.
When a program encounters something unexpected—like a failed network connection, corrupted data, or exhausted system resources—it must handle it gracefully. Improper exception handling means the software might crash, expose sensitive debugging information, or continue operating with incorrect assumptions, creating openings for attackers to exploit. To prevent this, developers should implement robust error handling that anticipates potential failure points. This includes using structured exception handling mechanisms, defining clear recovery procedures, validating all external inputs, and ensuring the application fails securely without leaking internal details that could aid an attacker.
Impacto en el mundo real

Real-world CVEs caused by CWE-755

  • CVE-2023-41151

    SDK for OPC Unified Architecture (OPC UA) server has uncaught exception when a socket is blocked for writing but the server tries to send an error

  • [REF-1374]

    Chain: JavaScript-based cryptocurrency library can fall back to the insecure Math.random() function instead of reporting a failure (CWE-392), thus reducing the entropy (CWE-332) and leading to generation of non-unique cryptographic keys for Bitcoin wallets (CWE-1391)

  • CVE-2021-3011

    virtual interrupt controller in a virtualization product allows crash of host by writing a certain invalid value to a register, which triggers a fatal error instead of returning an error code

  • CVE-2008-4302

    Chain: OS kernel does not properly handle a failure of a function call (CWE-755), leading to an unlock of a resource that was not locked (CWE-832), with resultant crash.

Cómo lo explotan los atacantes

Ruta del atacante paso a paso

  1. 1

    The following example attempts to resolve a hostname.

  2. 2

    A DNS lookup failure will cause the Servlet to throw an exception.

  3. 3

    The following example attempts to allocate memory for a character. After the call to malloc, an if statement is used to check whether the malloc function failed.

  4. 4

    The conditional successfully detects a NULL return value from malloc indicating a failure, however it does not do anything to handle the problem. Unhandled errors may have unexpected results and may cause the program to crash or terminate.

  5. 5

    Instead, the if block should contain statements that either attempt to fix the problem or notify the user that an error has occurred and continue processing or perform some cleanup and gracefully terminate the program. The following example notifies the user that the malloc function did not allocate the required memory resources and returns an error code.

Ejemplo de código vulnerable

Vulnerable Java

The following example attempts to resolve a hostname.

Vulnerable Java 
protected void doPost (HttpServletRequest req, HttpServletResponse res) throws IOException {
  	String ip = req.getRemoteAddr();
  	InetAddress addr = InetAddress.getByName(ip);
  	...
  	out.println("hello " + addr.getHostName());
  }
Ejemplo de código seguro

Secure C

Instead, the if block should contain statements that either attempt to fix the problem or notify the user that an error has occurred and continue processing or perform some cleanup and gracefully terminate the program. The following example notifies the user that the malloc function did not allocate the required memory resources and returns an error code.

Seguro C 
foo=malloc(sizeof(char)); //the next line checks to see if malloc failed
  if (foo==NULL) {
  	printf("Malloc failed to allocate memory resources");
  	return -1;
  }
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-755

  • 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-755

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-755 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-755?

This vulnerability occurs when software fails to properly manage unexpected situations or errors, leaving it in an unstable or insecure state.

¿Qué gravedad tiene CWE-755?

MITRE califica la probabilidad de explotación como Media — la explotación es realista pero suele requerir condiciones específicas.

¿Qué lenguajes o plataformas se ven afectados por CWE-755?

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

¿Cómo puedo prevenir CWE-755?

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-755?

El motor SAST de Plexicus detecta la firma de flujo de datos para CWE-755 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-755?

MITRE publica la definición canónica en https://cwe.mitre.org/data/definitions/755.html. También puedes consultar la documentación de OWASP y NIST para guías relacionadas.

Debilidades relacionadas

Weaknesses related to CWE-755

CWE-703 Padre

Improper Check or Handling of Exceptional Conditions

This vulnerability occurs when software fails to properly plan for or manage rare but possible error scenarios, leaving it unprepared for…

CWE-1384 Hermano

Improper Handling of Physical or Environmental Conditions

This weakness occurs when a hardware device fails to manage unexpected physical or environmental situations, whether they happen naturally…

CWE-228 Hermano

Improper Handling of Syntactically Invalid Structure

This vulnerability occurs when software fails to properly reject or process input that doesn't follow the expected format or structure,…

CWE-248 Hermano

Uncaught Exception

This vulnerability occurs when a function throws an error or exception, but the calling code does not have a proper handler to catch and…

CWE-391 Hermano

Unchecked Error Condition

This vulnerability occurs when a program fails to properly check or handle error conditions, such as exceptions or return codes. By…

CWE-392 Hermano

Missing Report of Error Condition

This vulnerability occurs when a system fails to properly signal that an error has happened. Instead of returning a clear error code,…

CWE-393 Hermano

Return of Wrong Status Code

This vulnerability occurs when a function returns an inaccurate status code or value that misrepresents the actual outcome of an…

CWE-397 Hermano

Declaration of Throws for Generic Exception

This vulnerability occurs when a method is declared to throw an overly broad exception type, such as a generic 'Exception' or 'Throwable'.…

CWE-754 Hermano

Improper Check for Unusual or Exceptional Conditions

This weakness occurs when software fails to properly anticipate and handle rare or unexpected runtime situations that fall outside normal…

Recursos

Further reading

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