CWE-158 Variante Incomplet

Improper Neutralization of Null Byte or NUL Character

This weakness occurs when an application receives data but fails to properly handle or remove NUL characters (\0) before passing that data to another system component.

Définition

What is CWE-158?

This weakness occurs when an application receives data but fails to properly handle or remove NUL characters (\0) before passing that data to another system component.
A NUL character (represented as '\0' or a zero byte) is a standard marker for the end of a string in many programming languages and systems. When an attacker injects this character into input data, the application may incorrectly interpret it as the end of the data, effectively ignoring any content that comes after it. This can trick validation checks or processing logic into seeing only a harmless first part of the input, while the dangerous payload hidden after the NUL byte gets passed through. This bypass is a classic technique for manipulating file paths, configuration strings, or command arguments. For instance, an attacker could submit a filename like "safe.txt\0malicious.php" to bypass extension filters that stop checking at the NUL, potentially leading to unauthorized file access or code execution. The core defense is to treat NUL characters as invalid data within the relevant context and to reject or sanitize inputs that contain them.
Impact réel

Real-world CVEs caused by CWE-158

  • CVE-2008-1284

    NUL byte in theme name causes directory traversal impact to be worse

  • CVE-2005-2008

    Source code disclosure using trailing null.

  • CVE-2005-3293

    Source code disclosure using trailing null.

  • CVE-2005-2061

    Trailing null allows file include.

  • CVE-2002-1774

    Null character in MIME header allows detection bypass.

  • CVE-2000-0149

    Web server allows remote attackers to view the source code for CGI programs via a null character (%00) at the end of a URL.

  • CVE-2000-0671

    Web server earlier allows allows remote attackers to bypass access restrictions, list directory contents, and read source code by inserting a null character (%00) in the URL.

  • CVE-2001-0738

    Logging system allows an attacker to cause a denial of service (hang) by causing null bytes to be placed in log messages.

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 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-158

  • Developers should anticipate that null characters or null bytes will be injected/removed/manipulated in the input vectors of their product. Use an appropriate combination of denylists and allowlists to ensure only valid, expected and appropriate input is processed by the system.
  • Implementation Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does. When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue." Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
  • Implementation Inputs should be decoded and canonicalized to the application's current internal representation before being validated (CWE-180). Make sure that the application does not decode the same input twice (CWE-174). Such errors could be used to bypass allowlist validation schemes by introducing dangerous inputs after they have been checked.
Signaux de détection

How to detect CWE-158

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-158 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-158 ?

This weakness occurs when an application receives data but fails to properly handle or remove NUL characters (\0) before passing that data to another system component.

Quelle est la gravité de CWE-158 ?

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-158 ?

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-158 ?

Developers should anticipate that null characters or null bytes will be injected/removed/manipulated in the input vectors of their product. Use an appropriate combination of denylists and allowlists to ensure only valid, expected and appropriate input is processed by the system. Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to…

Comment Plexicus détecte et corrige CWE-158 ?

Le moteur SAST de Plexicus reconnaît la signature de flux de données de CWE-158 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-158 ?

MITRE publie la définition canonique à https://cwe.mitre.org/data/definitions/158.html. Vous pouvez également consulter la documentation OWASP et NIST pour des conseils adjacents.

Faiblesses associées

Weaknesses related to CWE-158

CWE-138 Parent

Improper Neutralization of Special Elements

This vulnerability occurs when an application accepts external input but fails to properly sanitize special characters or syntax that have…

CWE-140 Frère

Improper Neutralization of Delimiters

This vulnerability occurs when an application fails to properly handle or sanitize delimiter characters within data inputs, allowing them…

CWE-147 Frère

Improper Neutralization of Input Terminators

This vulnerability occurs when an application accepts external input but fails to properly handle special characters that downstream…

CWE-148 Frère

Improper Neutralization of Input Leaders

This vulnerability occurs when an application fails to properly validate or handle input that begins with special control characters or…

CWE-149 Frère

Improper Neutralization of Quoting Syntax

This vulnerability occurs when an application fails to properly validate or escape quote characters (like single ' or double " quotes) in…

CWE-150 Frère

Improper Neutralization of Escape, Meta, or Control Sequences

This vulnerability occurs when an application fails to properly sanitize or escape special character sequences in user-supplied input…

CWE-151 Frère

Improper Neutralization of Comment Delimiters

This vulnerability occurs when an application accepts user input and fails to properly sanitize characters that can be interpreted as…

CWE-152 Frère

Improper Neutralization of Macro Symbols

This vulnerability occurs when an application accepts user input containing macro symbols (like those used in templates or configuration…

CWE-153 Frère

Improper Neutralization of Substitution Characters

This vulnerability occurs when an application accepts user input and fails to properly sanitize special characters that can trigger…

Ressources

Further reading

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