CWE-760: Use of a One-Way Hash with a Predictable Salt

Définition

What is CWE-760?

This vulnerability occurs when an application uses a one-way hash (like for password storage) but combines it with a predictable or easily guessed salt. This undermines the security benefit of salting, making pre-computed attack methods like rainbow tables highly effective.

Using a predictable salt, such as a username or a static string, allows attackers to bypass the primary defense salting provides. Attackers can pre-generate massive lookup tables (rainbow tables) for that specific salt, enabling them to quickly reverse hashes and recover credentials. This effectively nullifies the security advantage that a random, unique salt is meant to deliver. It's important to understand that even a strong, random salt is not a complete solution against determined attackers with significant resources, as hashing algorithms are designed for speed. Modern password cracking using cloud or specialized hardware can still be effective. For robust protection, consider adaptive, computationally expensive hash functions (like Argon2, scrypt, or bcrypt) designed specifically for passwords. Identifying and fixing these predictable salt patterns across a large codebase can be challenging; an ASPM platform like Plexicus can automatically detect such flaws via SAST and use AI to provide specific remediation guidance, streamlining the fix process.

Impact réel

Real-world CVEs caused by CWE-760

CVE-2008-4905

Blogging software uses a hard-coded salt when calculating a password hash.
CVE-2002-1657

Database server uses the username for a salt when encrypting passwords, simplifying brute force attacks.
CVE-2001-0967

Server uses a constant salt when encrypting passwords, simplifying brute force attacks.
CVE-2005-0408

chain: product generates predictable MD5 hashes using a constant value combined with username, allowing authentication bypass.

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 pseudo

MITRE n'a pas publié d'exemple de code pour ce CWE. Le motif ci-dessous est illustratif — voir Ressources pour les références canoniques.

Vulnérable pseudo

// Example pattern — see MITRE for the canonical references.
function handleRequest(input) {
  // Untrusted input flows directly into the sensitive sink.
  return executeUnsafe(input);
}

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-760

Architecture and Design Use an adaptive hash function that can be configured to change the amount of computational effort needed to compute the hash, such as the number of iterations ("stretching") or the amount of memory required. Some hash functions perform salting automatically. These functions can significantly increase the overhead for a brute force attack compared to intentionally-fast functions such as MD5. For example, rainbow table attacks can become infeasible due to the high computing overhead. Finally, since computing power gets faster and cheaper over time, the technique can be reconfigured to increase the workload without forcing an entire replacement of the algorithm in use. Some hash functions that have one or more of these desired properties include bcrypt [REF-291], scrypt [REF-292], and PBKDF2 [REF-293]. While there is active debate about which of these is the most effective, they are all stronger than using salts with hash functions with very little computing overhead. Note that using these functions can have an impact on performance, so they require special consideration to avoid denial-of-service attacks. However, their configurability provides finer control over how much CPU and memory is used, so it could be adjusted to suit the environment's needs.
Implementation If a technique that requires extra computational effort can not be implemented, then for each password that is processed, generate a new random salt using a strong random number generator with unpredictable seeds. Add the salt to the plaintext password before hashing it. When storing the hash, also store the salt. Do not use the same salt for every password.

Signaux de détection

How to detect CWE-760

Automated Static Analysis High

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-760

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Questions fréquentes

Frequently asked questions

Qu'est-ce que CWE-760 ?

This vulnerability occurs when an application uses a one-way hash (like for password storage) but combines it with a predictable or easily guessed salt. This undermines the security benefit of salting, making pre-computed attack methods like rainbow tables highly effective.

Quelle est la gravité de CWE-760 ?

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-760 ?

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-760 ?

Use an adaptive hash function that can be configured to change the amount of computational effort needed to compute the hash, such as the number of iterations ("stretching") or the amount of memory required. Some hash functions perform salting automatically. These functions can significantly increase the overhead for a brute force attack compared to intentionally-fast functions such as MD5. For example, rainbow table attacks can become infeasible due to the high computing overhead. Finally,…

Comment Plexicus détecte et corrige CWE-760 ?

Le moteur SAST de Plexicus reconnaît la signature de flux de données de CWE-760 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-760 ?

MITRE publie la définition canonique à https://cwe.mitre.org/data/definitions/760.html. Vous pouvez également consulter la documentation OWASP et NIST pour des conseils adjacents.

Faiblesses associées

Weaknesses related to CWE-760

CWE-916 Parent

Use of Password Hash With Insufficient Computational Effort

This vulnerability occurs when a system protects passwords by hashing them, but uses a hashing algorithm that is too fast or…

CWE-759 Frère

Use of a One-Way Hash without a Salt

This vulnerability occurs when a system uses a one-way hash function (like MD5 or SHA-256) to protect sensitive data like passwords, but…

Ressources

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Use of a One-Way Hash with a Predictable Salt