CWE-289 Base Incomplet

Authentication Bypass by Alternate Name

This vulnerability occurs when a system checks access based on a resource or user name, but fails to account for all the different names or aliases that could refer to the same entity, allowing…

Définition

What is CWE-289?

This vulnerability occurs when a system checks access based on a resource or user name, but fails to account for all the different names or aliases that could refer to the same entity, allowing attackers to bypass authentication.
This flaw often appears in systems that rely on simple string matching for access control. For example, a file server might block access to 'admin.txt' but overlook 'ADMIN.TXT', 'Admin.Txt', or a symlink pointing to the same file. Similarly, a user authentication system might verify 'administrator' but not check for 'admin', 'root', or other common aliases for privileged accounts. Attackers exploit this by simply using an alternate name the system doesn't recognize as restricted. To prevent this, developers must implement canonicalization, where all names are resolved to a single, standard form before the security check. This means normalizing file paths, converting usernames to a consistent case, and resolving symbolic links. Access control logic should never rely on raw, unvalidated input strings. Instead, it should compare the canonical identity of the resource or user against a policy that is enforced consistently for all access attempts.
Impact réel

Real-world CVEs caused by CWE-289

  • CVE-2003-0317

    Protection mechanism that restricts URL access can be bypassed using URL encoding.

  • CVE-2004-0847

    Bypass of authentication for files using "\" (backslash) or "%5C" (encoded backslash).

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-289

  • Architecture and Design Avoid making decisions based on names of resources (e.g. files) if those resources can have alternate names.
  • 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-289

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-289 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-289 ?

This vulnerability occurs when a system checks access based on a resource or user name, but fails to account for all the different names or aliases that could refer to the same entity, allowing attackers to bypass authentication.

Quelle est la gravité de CWE-289 ?

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-289 ?

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-289 ?

Avoid making decisions based on names of resources (e.g. files) if those resources can have alternate names. 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…

Comment Plexicus détecte et corrige CWE-289 ?

Le moteur SAST de Plexicus reconnaît la signature de flux de données de CWE-289 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-289 ?

MITRE publie la définition canonique à https://cwe.mitre.org/data/definitions/289.html. Vous pouvez également consulter la documentation OWASP et NIST pour des conseils adjacents.

Faiblesses associées

Weaknesses related to CWE-289

CWE-1390 Parent

Weak Authentication

This vulnerability occurs when a system's login or identity verification process is too easy to bypass or fool. While it attempts to check…

CWE-1391 Frère

Use of Weak Credentials

This vulnerability occurs when a system relies on weak authentication credentials—like default passwords, hard-coded keys, or easily…

CWE-262 Frère

Not Using Password Aging

This vulnerability occurs when a system lacks password expiration policies, allowing users to keep the same password indefinitely.

CWE-263 Frère

Password Aging with Long Expiration

The system enforces password changes, but the time allowed between changes is excessively long, weakening security.

CWE-290 Frère

Authentication Bypass by Spoofing

This weakness occurs when an application's authentication system can be tricked into accepting forged or manipulated credentials, allowing…

CWE-294 Frère

Authentication Bypass by Capture-replay

This vulnerability occurs when an attacker can intercept and record legitimate authentication traffic, then replay it later to gain…

CWE-301 Frère

Reflection Attack in an Authentication Protocol

A reflection attack is a flaw in mutual authentication protocols that allows an attacker to impersonate a legitimate user without knowing…

CWE-302 Frère

Authentication Bypass by Assumed-Immutable Data

This vulnerability occurs when an authentication system incorrectly treats certain data as unchangeable, when in fact an attacker can…

CWE-303 Frère

Incorrect Implementation of Authentication Algorithm

This weakness occurs when a developer implements a standard authentication algorithm, but makes critical mistakes in the code that cause…

Ressources

Further reading

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