Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc.)
CWE-338 Base Brouillon
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 security-sensitive operations, such as generating keys, tokens, or…
Définition
What is CWE-338?
This vulnerability occurs when software uses a pseudo-random number generator (PRNG) that is not cryptographically strong for security-sensitive operations, such as generating keys, tokens, or initialization vectors.
Using a non-cryptographic PRNG in a security context can expose your application to attacks. Attackers can often predict or reproduce the generated numbers, allowing them to forge sessions, decrypt data, or bypass authentication. This happens because these generators prioritize speed and efficiency over the unpredictability required for secure cryptography.
Developers sometimes choose weaker PRNGs for performance reasons or because they are readily available in standard libraries. However, features that make these PRNGs efficient—like small internal states or deterministic seeding—are the same features that make them easy to break. For any security-related function, you must use a cryptographically secure pseudo-random number generator (CSPRNG) designed to withstand such analysis.
Impact réel
Real-world CVEs caused by CWE-338
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PHP framework uses mt_rand() function (Marsenne Twister) when generating tokens
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Crypto product uses rand() library function to generate a recovery key, making it easier to conduct brute force attacks.
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Random number generator can repeatedly generate the same value.
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Web application generates predictable session IDs, allowing session hijacking.
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SSL library uses a weak random number generator that only generates 65,536 unique keys.
Comment les attaquants l'exploitent
Parcours de l'attaquant étape par étape
- 1
Identifier un chemin de code qui traite des entrées non fiables sans validation.
- 2
Élaborer une charge utile qui exploite le comportement non sécurisé — injection, traversal, débordement ou abus de logique.
- 3
Délivrer la charge utile via une requête normale et observer la réaction de l'application.
- 4
Itérer jusqu'à ce que la réponse divulgue des données, exécute le code de l'attaquant ou élève les privilèges.
Exemple de code vulnérable
Vulnerable Java
Both of these examples use a statistical PRNG seeded with the current value of the system clock to generate a random number:
Random random = new Random(System.currentTimeMillis());
int accountID = random.nextInt(); Exemple de code sécurisé
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.
Liste de contrôle de prévention
How to prevent CWE-338
- Implementation Use functions or hardware which use a hardware-based random number generation for all crypto. This is the recommended solution. Use CyptGenRandom on Windows, or hw_rand() on Linux.
Signaux de détection
How to detect CWE-338
CWE-338
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Questions fréquentes Qu'est-ce que CWE-338 ?
Quelle est la gravité de CWE-338 ?
Quels langages ou plateformes sont affectés par CWE-338 ?
Comment puis-je prévenir CWE-338 ?
Comment Plexicus détecte et corrige CWE-338 ?
Où puis-je en savoir plus sur CWE-338 ?
Frequently asked questions
Qu'est-ce que CWE-338 ?
This vulnerability occurs when software uses a pseudo-random number generator (PRNG) that is not cryptographically strong for security-sensitive operations, such as generating keys, tokens, or initialization vectors.
Quelle est la gravité de CWE-338 ?
MITRE évalue la probabilité d'exploitation comme Moyenne — l'exploitation est réaliste mais nécessite généralement des conditions spécifiques.
Quels langages ou plateformes sont affectés par CWE-338 ?
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-338 ?
Use functions or hardware which use a hardware-based random number generation for all crypto. This is the recommended solution. Use CyptGenRandom on Windows, or hw_rand() on Linux.
Comment Plexicus détecte et corrige CWE-338 ?
Le moteur SAST de Plexicus reconnaît la signature de flux de données de CWE-338 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-338 ?
MITRE publie la définition canonique à https://cwe.mitre.org/data/definitions/338.html. Vous pouvez également consulter la documentation OWASP et NIST pour des conseils adjacents.
Faiblesses associées
Weaknesses related to CWE-338
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-335 Frère
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-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…
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