CWE-334 Base Borrador

Small Space of Random Values

This vulnerability occurs when a system uses a random number generator that produces too few possible values. Attackers can easily predict or guess these values through brute force attacks.

Definición

What is CWE-334?

This vulnerability occurs when a system uses a random number generator that produces too few possible values. Attackers can easily predict or guess these values through brute force attacks.
When an application relies on random values for security—like generating session tokens, encryption keys, or password reset codes—using a random source with a small output space is a critical flaw. For example, a random number generator that only produces 65,536 possible values (16 bits) is trivial for an automated script to exhaustively try all combinations. This directly undermines security mechanisms designed to be unpredictable. To prevent this, developers must ensure their random value generators have an output space large enough to resist brute-force attempts for the required lifespan of the secret. This typically means using cryptographically secure pseudo-random number generators (CSPRNGs) that produce values with at least 128 bits of entropy. Always match the randomness strength to the sensitivity of the operation it protects.
Impacto en el mundo real

Real-world CVEs caused by CWE-334

  • CVE-2002-0583

    Product uses 5 alphanumeric characters for filenames of expense claim reports, stored under web root.

  • CVE-2002-0903

    Product uses small number of random numbers for a code to approve an action, and also uses predictable new user IDs, allowing attackers to hijack new accounts.

  • CVE-2003-1230

    SYN cookies implementation only uses 32-bit keys, making it easier to brute force ISN.

  • CVE-2004-0230

    Complex predictability / randomness (reduced space).

Cómo lo explotan los atacantes

Ruta del atacante paso a paso

  1. 1

    The following XML example code is a deployment descriptor for a Java web application deployed on a Sun Java Application Server. This deployment descriptor includes a session configuration property for configuring the session ID length.

  2. 2

    This deployment descriptor has set the session ID length for this Java web application to 8 bytes (or 64 bits). The session ID length for Java web applications should be set to 16 bytes (128 bits) to prevent attackers from guessing and/or stealing a session ID and taking over a user's session.

  3. 3

    Note for most application servers including the Sun Java Application Server the session ID length is by default set to 128 bits and should not be changed. And for many application servers the session ID length cannot be changed from this default setting. Check your application server documentation for the session ID length default setting and configuration options to ensure that the session ID length is set to 128 bits.

Ejemplo de código vulnerable

Vulnerable XML

The following XML example code is a deployment descriptor for a Java web application deployed on a Sun Java Application Server. This deployment descriptor includes a session configuration property for configuring the session ID length.

Vulnerable XML 
<sun-web-app>
  		...
  		<session-config>
  				<session-properties>
  					<property name="idLengthBytes" value="8">
  						<description>The number of bytes in this web module's session ID.</description>
  					</property>
  				</session-properties>
  		</session-config>
  		...
  </sun-web-app>
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-334

  • Architecture and Design / Requirements Use products or modules that conform to FIPS 140-2 [REF-267] to avoid obvious entropy problems. Consult FIPS 140-2 Annex C ("Approved Random Number Generators").
Señales de detección

How to detect CWE-334

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-334 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-334?

This vulnerability occurs when a system uses a random number generator that produces too few possible values. Attackers can easily predict or guess these values through brute force attacks.

¿Qué gravedad tiene CWE-334?

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-334?

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

¿Cómo puedo prevenir CWE-334?

Use products or modules that conform to FIPS 140-2 [REF-267] to avoid obvious entropy problems. Consult FIPS 140-2 Annex C ("Approved Random Number Generators").

¿Cómo detecta y corrige Plexicus CWE-334?

El motor SAST de Plexicus detecta la firma de flujo de datos para CWE-334 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-334?

MITRE publica la definición canónica en https://cwe.mitre.org/data/definitions/334.html. También puedes consultar la documentación de OWASP y NIST para guías relacionadas.

Debilidades relacionadas

Weaknesses related to CWE-334

CWE-330 Padre

Use of Insufficiently Random Values

This vulnerability occurs when an application uses random values that are not sufficiently unpredictable in security-sensitive operations,…

CWE-1204 Hermano

Generation of Weak Initialization Vector (IV)

This vulnerability occurs when software uses a weak or predictable Initialization Vector (IV) for cryptographic operations. Many…

CWE-1241 Hermano

Use of Predictable Algorithm in Random Number Generator

This vulnerability occurs when a device or application relies on a predictable algorithm to generate pseudo-random numbers, making the…

CWE-331 Hermano

Insufficient Entropy

This vulnerability occurs when a system's random number generator or algorithm lacks sufficient unpredictability, creating patterns or…

CWE-335 Hermano

Incorrect Usage of Seeds in Pseudo-Random Number Generator (PRNG)

This vulnerability occurs when a Pseudo-Random Number Generator (PRNG) is used, but its initial seed value is not handled securely or…

CWE-338 Hermano

Use of Cryptographically Weak Pseudo-Random Number Generator (PRNG)

This vulnerability occurs when software uses a pseudo-random number generator (PRNG) that is not cryptographically strong for…

CWE-340 Hermano

Generation of Predictable Numbers or Identifiers

This vulnerability occurs when a system creates numbers or identifiers that are too easy to guess, undermining security mechanisms that…

CWE-344 Hermano

Use of Invariant Value in Dynamically Changing Context

This vulnerability occurs when code uses a fixed, unchanging value (like a hardcoded string, number, or reference) in a situation where…

CWE-6 Hijo

J2EE Misconfiguration: Insufficient Session-ID Length

This vulnerability occurs when a J2EE application uses session identifiers that are too short, making them easier for attackers to predict…

Recursos

Further reading

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