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CWE-335 Base Borrador
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 predictably, compromising the randomness of its output.
Definición
What is CWE-335?
This vulnerability occurs when a Pseudo-Random Number Generator (PRNG) is used, but its initial seed value is not handled securely or predictably, compromising the randomness of its output.
PRNGs are not truly random; they are deterministic algorithms that produce a sequence of numbers based on an initial seed. If an attacker can discover or guess this seed, they can predict the entire output stream, which is catastrophic for security functions like encryption keys, session tokens, or cryptographic nonces. Therefore, the seed must be treated with the same secrecy as a cryptographic key and should be generated from a robust, unpredictable source.
Secure seed management involves two critical practices. First, protect the seed itself as sensitive material—never hard-code it, log it, or transmit it insecurely. Second, source the seed from a cryptographically secure random number generator (CSPRNG) provided by the operating system or trusted library to ensure sufficient entropy. Avoid using predictable values like the current time, process IDs, or static strings, as these drastically reduce the number of possible seeds an attacker would need to guess.
Impacto en el mundo real
Real-world CVEs caused by CWE-335
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Cloud application on Kubernetes generates passwords using a weak random number generator based on deployment time.
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server uses erlang:now() to seed the PRNG, which results in a small search space for potential random seeds
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Product's PRNG is not seeded for the generation of session IDs
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Router's PIN generation is based on rand(time(0)) seeding.
Cómo lo explotan los atacantes
Ruta del atacante paso a paso
- 1
The following code uses a statistical PRNG to generate account IDs.
- 2
Because the program uses the same seed value for every invocation of the PRNG, its values are predictable, making the system vulnerable to attack.
- 3
Both of these examples use a statistical PRNG seeded with the current value of the system clock to generate a random number:
- 4
An attacker can easily predict the seed used by these PRNGs, and so also predict the stream of random numbers generated. Note these examples also exhibit CWE-338 (Use of Cryptographically Weak PRNG).
- 5
This code grabs some random bytes and uses them for a seed in a PRNG, in order to generate a new cryptographic key.
Ejemplo de código vulnerable
Vulnerable Java
The following code uses a statistical PRNG to generate account IDs.
private static final long SEED = 1234567890;
public int generateAccountID() {
Random random = new Random(SEED);
return random.nextInt();
} 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-335
- 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-335
Ejecuta pruebas dinámicas de seguridad de aplicaciones (DAST) contra el endpoint en vivo.
Vigila los logs en tiempo de ejecución para detectar trazas de excepción inusuales, entradas malformadas o intentos de bypass de autorización.
Revisión de código: marca cualquier código nuevo que maneje entrada desde esta superficie sin usar los helpers validados del framework.
Plexicus detecta automáticamente CWE-335 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-335?
¿Qué gravedad tiene CWE-335?
¿Qué lenguajes o plataformas se ven afectados por CWE-335?
¿Cómo puedo prevenir CWE-335?
¿Cómo detecta y corrige Plexicus CWE-335?
¿Dónde puedo aprender más sobre CWE-335?
Frequently asked questions
¿Qué es CWE-335?
This vulnerability occurs when a Pseudo-Random Number Generator (PRNG) is used, but its initial seed value is not handled securely or predictably, compromising the randomness of its output.
¿Qué gravedad tiene CWE-335?
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-335?
MITRE no ha especificado plataformas afectadas para esta CWE — puede aplicar a la mayoría de los stacks de aplicaciones.
¿Cómo puedo prevenir CWE-335?
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-335?
El motor SAST de Plexicus detecta la firma de flujo de datos para CWE-335 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-335?
MITRE publica la definición canónica en https://cwe.mitre.org/data/definitions/335.html. También puedes consultar la documentación de OWASP y NIST para guías relacionadas.
Debilidades relacionadas
Weaknesses related to CWE-335
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-334 Hermano
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…
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-336 Hijo
Same Seed in Pseudo-Random Number Generator (PRNG)
This vulnerability occurs when a Pseudo-Random Number Generator (PRNG) is repeatedly initialized with the same starting seed value.
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