Fuzz testing (fuzzing) is a powerful technique for generating large numbers of diverse inputs - either randomly or algorithmically - and dynamically invoking the code with those inputs. Even with random inputs, it is often capable of generating unexpected results such as crashes, memory corruption, or resource consumption. Fuzzing effectively produces repeatable test cases that clearly indicate bugs, which helps developers to diagnose the issues.
CWE-393 Base Borrador
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 operation. This false signal can cause the application to behave in…
Definición
What is CWE-393?
This vulnerability occurs when a function returns an inaccurate status code or value that misrepresents the actual outcome of an operation. This false signal can cause the application to behave in unexpected and potentially insecure ways.
When a system relies on these incorrect return codes to make decisions, it can lead to unpredictable application states, logic errors, and instability. For example, a function might incorrectly report a successful file deletion or a failed authentication check, causing the program flow to proceed down the wrong path.
If these status checks are part of security-critical logic—like access control, authentication, or data validation—the consequences are severe. The application might grant access to unauthorized users, assume a dangerous operation succeeded safely, or fail to alert on genuine security failures, creating hidden vulnerabilities that attackers can exploit.
Impacto en el mundo real
Real-world CVEs caused by CWE-393
-
DNS server returns wrong response code for non-existent AAAA record, which effectively says that the domain is inaccessible.
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Hardware-specific implementation of system call causes incorrect results from geteuid.
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Chain: System call returns wrong value (CWE-393), leading to a resultant NULL dereference (CWE-476).
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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
Identifica una ruta de código que maneje entrada no confiable sin validación.
- 2
Crea un payload que ejercite el comportamiento inseguro — inyección, traversal, overflow o abuso de lógica.
- 3
Envía el payload a través de una solicitud normal y observa la reacción de la aplicación.
- 4
Itera hasta que la respuesta filtre datos, ejecute código del atacante o escale privilegios.
Ejemplo de código vulnerable
Vulnerable Java
In the following example, an HTTP 404 status code is returned in the event of an IOException encountered in a Java servlet. A 404 code is typically meant to indicate a non-existent resource and would be somewhat misleading in this case.
try {
```
// something that might throw IOException*
...} catch (IOException ioe) {
```
response.sendError(SC_NOT_FOUND);
} Ejemplo de código seguro
Secure 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-393
- 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-393
CWE-393
Don't catalog this weakness. Prove it's reachable.
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Preguntas frecuentes ¿Qué es CWE-393?
¿Qué gravedad tiene CWE-393?
¿Qué lenguajes o plataformas se ven afectados por CWE-393?
¿Cómo puedo prevenir CWE-393?
¿Cómo detecta y corrige Plexicus CWE-393?
¿Dónde puedo aprender más sobre CWE-393?
Frequently asked questions
¿Qué es CWE-393?
This vulnerability occurs when a function returns an inaccurate status code or value that misrepresents the actual outcome of an operation. This false signal can cause the application to behave in unexpected and potentially insecure ways.
¿Qué gravedad tiene CWE-393?
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-393?
MITRE no ha especificado plataformas afectadas para esta CWE — puede aplicar a la mayoría de los stacks de aplicaciones.
¿Cómo puedo prevenir CWE-393?
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-393?
El motor SAST de Plexicus detecta la firma de flujo de datos para CWE-393 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-393?
MITRE publica la definición canónica en https://cwe.mitre.org/data/definitions/393.html. También puedes consultar la documentación de OWASP y NIST para guías relacionadas.
Debilidades relacionadas
Weaknesses related to CWE-393
CWE-684 Padre
Incorrect Provision of Specified Functionality
This weakness occurs when software behaves differently than its documented specifications, which can mislead users and create security…
CWE-1245 Hermano
Improper Finite State Machines (FSMs) in Hardware Logic
This vulnerability occurs when hardware logic contains flawed Finite State Machines (FSMs). Attackers can exploit these design errors to…
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-440 Hermano
Expected Behavior Violation
This weakness occurs when a software component, such as a function, API, or feature, fails to act as documented or intended. The system's…
CWE-446 Hermano
UI Discrepancy for Security Feature
This vulnerability occurs when a user interface incorrectly displays a security feature as active or properly configured, misleading users…
CWE-451 Hermano
User Interface (UI) Misrepresentation of Critical Information
This vulnerability occurs when a user interface fails to accurately display or highlight crucial information, potentially misleading users…
CWE-912 Hermano
Hidden Functionality
Hidden functionality refers to undocumented features, commands, or code within a product that are not part of its official specification…
¿Listo para validar lo que importa?
Listo para validar lo que importa.
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