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-704 Clase Incompleto
Incorrect Type Conversion or Cast
This vulnerability occurs when software incorrectly changes data from one type to another, leading to unexpected behavior or security flaws.
Definición
What is CWE-704?
This vulnerability occurs when software incorrectly changes data from one type to another, leading to unexpected behavior or security flaws.
Incorrect type conversion, often called a type confusion or type casting bug, happens when a developer assumes a piece of data is one kind of object or structure (like an integer, string, or class instance) but the program treats it as another. This mismatch can cause the application to misinterpret the data's meaning, access the wrong memory locations, or call incorrect functions, which attackers can exploit to crash the system, leak information, or execute arbitrary code.
These issues are common in languages that allow manual type casting (like C/C++) or have weak typing, but they can also appear in higher-level languages during serialization, inter-process communication, or when using reflection. To prevent this, developers should validate data types before conversion, use safe casting functions provided by the language, and implement strict input validation at all system boundaries.
Impacto en el mundo real
Real-world CVEs caused by CWE-704
-
Chain: in a web browser, an unsigned 64-bit integer is forcibly cast to a 32-bit integer (CWE-681) and potentially leading to an integer overflow (CWE-190). If an integer overflow occurs, this can cause heap memory corruption (CWE-122)
-
Chain: data visualization program written in PHP uses the "!=" operator instead of the type-strict "!==" operator (CWE-480) when validating hash values, potentially leading to an incorrect type conversion (CWE-704)
Cómo lo explotan los atacantes
Ruta del atacante paso a paso
- 1
In this example, depending on the return value of accecssmainframe(), the variable amount can hold a negative value when it is returned. Because the function is declared to return an unsigned value, amount will be implicitly cast to an unsigned number.
- 2
If the return value of accessmainframe() is -1, then the return value of readdata() will be 4,294,967,295 on a system that uses 32-bit integers.
- 3
The following code uses a union to support the representation of different types of messages. It formats messages differently, depending on their type.
- 4
The code intends to process the message as a NAME_TYPE, and sets the default message to "Hello World." However, since both buf.name and buf.nameID are part of the same union, they can act as aliases for the same memory location, depending on memory layout after compilation.
- 5
As a result, modification of buf.nameID - an int - can effectively modify the pointer that is stored in buf.name - a string.
Ejemplo de código vulnerable
Vulnerable C
In this example, depending on the return value of accecssmainframe(), the variable amount can hold a negative value when it is returned. Because the function is declared to return an unsigned value, amount will be implicitly cast to an unsigned number.
unsigned int readdata () {
int amount = 0;
...
amount = accessmainframe();
...
return amount;
} 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-704
- 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-704
Plexicus detecta automáticamente CWE-704 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.
Preguntas frecuentes ¿Qué es CWE-704?
¿Qué gravedad tiene CWE-704?
¿Qué lenguajes o plataformas se ven afectados por CWE-704?
¿Cómo puedo prevenir CWE-704?
¿Cómo detecta y corrige Plexicus CWE-704?
¿Dónde puedo aprender más sobre CWE-704?
Frequently asked questions
¿Qué es CWE-704?
This vulnerability occurs when software incorrectly changes data from one type to another, leading to unexpected behavior or security flaws.
¿Qué gravedad tiene CWE-704?
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-704?
MITRE lists the following affected platforms: C, C++.
¿Cómo puedo prevenir CWE-704?
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-704?
El motor SAST de Plexicus detecta la firma de flujo de datos para CWE-704 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-704?
MITRE publica la definición canónica en https://cwe.mitre.org/data/definitions/704.html. También puedes consultar la documentación de OWASP y NIST para guías relacionadas.
Debilidades relacionadas
Weaknesses related to CWE-704
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Reliance on Component That is Not Updateable
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CWE-221 Hermano
Information Loss or Omission
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CWE-404 Hermano
Improper Resource Shutdown or Release
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