CWE-335 Base Brouillon

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.

Définition

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.
Impact réel

Real-world CVEs caused by CWE-335

  • CVE-2020-7010

    Cloud application on Kubernetes generates passwords using a weak random number generator based on deployment time.

  • CVE-2019-11495

    server uses erlang:now() to seed the PRNG, which results in a small search space for potential random seeds

  • CVE-2018-12520

    Product's PRNG is not seeded for the generation of session IDs

  • CVE-2016-10180

    Router's PIN generation is based on rand(time(0)) seeding.

Comment les attaquants l'exploitent

Parcours de l'attaquant étape par étape

  1. 1

    The following code uses a statistical PRNG to generate account IDs.

  2. 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. 3

    Both of these examples use a statistical PRNG seeded with the current value of the system clock to generate a random number:

  4. 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. 5

    This code grabs some random bytes and uses them for a seed in a PRNG, in order to generate a new cryptographic key.

Exemple de code vulnérable

Vulnerable Java

The following code uses a statistical PRNG to generate account IDs.

Vulnérable Java 
private static final long SEED = 1234567890;
  public int generateAccountID() {
  	Random random = new Random(SEED);
  	return random.nextInt();
  }
Exemple de code sécurisé

Secure pseudo

Sécurisé 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.
Liste de contrôle de prévention

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.
Signaux de détection

How to detect CWE-335

SAST High

Exécuter une analyse statique (SAST) sur le code source à la recherche du motif non sécurisé dans le flux de données.

DAST Moderate

Exécuter des tests de sécurité applicative dynamique (DAST) contre le point de terminaison en ligne.

Runtime Moderate

Surveiller les journaux runtime pour détecter des traces d'exception inhabituelles, des entrées malformées ou des tentatives de contournement d'autorisation.

Code review Moderate

Revue de code : signaler tout nouveau code qui traite les entrées de cette surface sans utiliser les helpers du framework validés.

Correction automatique Plexicus

Plexicus détecte automatiquement CWE-335 et ouvre une PR de correction en moins de 60 secondes.

Codex Remedium analyse chaque commit, identifie cette faiblesse précise et livre une pull request prête à être relue avec le correctif. Pas de tickets. Pas de transferts.

Obtenir une démo Essayer Plexicus gratuitement
Questions fréquentes

Frequently asked questions

Qu'est-ce que 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.

Quelle est la gravité de CWE-335 ?

MITRE n'a pas publié de note de probabilité d'exploitation pour cette faiblesse. Traitez-la comme un impact moyen jusqu'à ce que votre modèle de menace prouve le contraire.

Quels langages ou plateformes sont affectés par CWE-335 ?

MITRE n'a pas spécifié les plateformes affectées pour ce CWE — il peut s'appliquer à la plupart des stacks applicatives.

Comment puis-je prévenir 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.

Comment Plexicus détecte et corrige CWE-335 ?

Le moteur SAST de Plexicus reconnaît la signature de flux de données de CWE-335 à chaque commit. Lorsqu'une correspondance est trouvée, notre agent Codex Remedium ouvre une PR de correction avec le code corrigé, les tests et un résumé d'une ligne pour le relecteur.

Où puis-je en savoir plus sur CWE-335 ?

MITRE publie la définition canonique à https://cwe.mitre.org/data/definitions/335.html. Vous pouvez également consulter la documentation OWASP et NIST pour des conseils adjacents.

Faiblesses associées

Weaknesses related to CWE-335

CWE-330 Parent

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 Frère

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 Frère

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 Frère

Insufficient Entropy

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

CWE-334 Frère

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 Frère

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 Frère

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 Frère

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 Enfant

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.

Ressources

Further reading

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