CWE-184 Base Brouillon

Incomplete List of Disallowed Inputs

This vulnerability occurs when a security filter or validation mechanism relies on a 'denylist'—a predefined list of forbidden inputs—but that list is missing critical entries. Attackers can bypass…

Définition

What is CWE-184?

This vulnerability occurs when a security filter or validation mechanism relies on a 'denylist'—a predefined list of forbidden inputs—but that list is missing critical entries. Attackers can bypass the protection by using variations or inputs the developers didn't anticipate.
Denylist-based security is fundamentally fragile because it requires developers to predict and block every possible bad input. This approach often fails against sophisticated attacks, as attackers constantly evolve their techniques to use new encodings, character sequences, or command variations that aren't on the list. Relying solely on a denylist creates a false sense of security and is difficult to maintain over time. For stronger protection, prioritize 'allowlisting' (only permitting known-good patterns) over denylisting. If a denylist is unavoidable, complement it with other defenses like strict input validation, output encoding, and security libraries designed to handle the specific threat. Always assume your denylist is incomplete and design your system to fail safely when an unexpected input is encountered.
Vulnerability Diagram CWE-184
Incomplete Blocklist Block list <script> ✗ <SCRIPT> ? <ScRiPt> ? <img onerror> ? javascript: ? Bypass payloads <ScRiPt>…</ScRiPt> <img src=x onerror=…> SELECT/**/* FROM ..%2f..%2fetc Reaches sink XSS / SQLi / traversal still works Denylists miss case, encoding and equivalent forms — use allowlists.
Impact réel

Real-world CVEs caused by CWE-184

  • CVE-2024-4315

    Chain: API for text generation using Large Language Models (LLMs) does not include the "\" Windows folder separator in its denylist (CWE-184) when attempting to prevent Local File Inclusion via path traversal (CWE-22), allowing deletion of arbitrary files on Windows systems.

  • CVE-2008-2309

    product uses a denylist to identify potentially dangerous content, allowing attacker to bypass a warning

  • CVE-2005-2782

    PHP remote file inclusion in web application that filters "http" and "https" URLs, but not "ftp".

  • CVE-2004-0542

    Programming language does not filter certain shell metacharacters in Windows environment.

  • CVE-2004-0595

    XSS filter doesn't filter null characters before looking for dangerous tags, which are ignored by web browsers. MIE and validate-before-cleanse.

  • CVE-2005-3287

    Web-based mail product doesn't restrict dangerous extensions such as ASPX on a web server, even though others are prohibited.

  • CVE-2004-2351

    Resultant XSS when only and are checked.

  • CVE-2005-2959

    Privileged program does not clear sensitive environment variables that are used by bash. Overlaps multiple interpretation error.

Comment les attaquants l'exploitent

Parcours de l'attaquant étape par étape

  1. 1

    Identifier un chemin de code qui traite des entrées non fiables sans validation.

  2. 2

    Élaborer une charge utile qui exploite le comportement non sécurisé — injection, traversal, débordement ou abus de logique.

  3. 3

    Délivrer la charge utile via une requête normale et observer la réaction de l'application.

  4. 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

The following code attempts to stop XSS attacks by removing all occurences of "script" in an input string.

Vulnérable Java 
public String removeScriptTags(String input, String mask) {
  	return input.replaceAll("script", mask);
  }
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-184

  • Implementation Do not rely exclusively on detecting disallowed inputs. There are too many variants to encode a character, especially when different environments are used, so there is a high likelihood of missing some variants. Only use detection of disallowed inputs as a mechanism for detecting suspicious activity. Ensure that you are using other protection mechanisms that only identify "good" input - such as lists of allowed inputs - and ensure that you are properly encoding your outputs.
Signaux de détection

How to detect CWE-184

Black Box

Exploitation of a vulnerability with commonly-used manipulations might fail, but minor variations might succeed.

Correction automatique Plexicus

Plexicus détecte automatiquement CWE-184 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-184 ?

This vulnerability occurs when a security filter or validation mechanism relies on a 'denylist'—a predefined list of forbidden inputs—but that list is missing critical entries. Attackers can bypass the protection by using variations or inputs the developers didn't anticipate.

Quelle est la gravité de CWE-184 ?

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-184 ?

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-184 ?

Do not rely exclusively on detecting disallowed inputs. There are too many variants to encode a character, especially when different environments are used, so there is a high likelihood of missing some variants. Only use detection of disallowed inputs as a mechanism for detecting suspicious activity. Ensure that you are using other protection mechanisms that only identify "good" input - such as lists of allowed inputs - and ensure that you are properly encoding your outputs.

Comment Plexicus détecte et corrige CWE-184 ?

Le moteur SAST de Plexicus reconnaît la signature de flux de données de CWE-184 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-184 ?

MITRE publie la définition canonique à https://cwe.mitre.org/data/definitions/184.html. Vous pouvez également consulter la documentation OWASP et NIST pour des conseils adjacents.

Faiblesses associées

Weaknesses related to CWE-184

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Ressources

Further reading

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