CWE-271 Classe Incomplet High likelihood

Privilege Dropping / Lowering Errors

This vulnerability occurs when a system or process fails to reduce its elevated permissions before transferring control of a resource to a less-privileged user or component.

Définition

What is CWE-271?

This vulnerability occurs when a system or process fails to reduce its elevated permissions before transferring control of a resource to a less-privileged user or component.
In secure software design, a common practice is for a high-privilege process to perform a sensitive operation and then immediately lower its permissions before interacting with lower-privileged entities. This flaw breaks that chain of trust. When a system hands off a file, process, or network connection without first dropping these elevated rights, it effectively grants those high-level permissions to the receiving party, which may not be authorized to have them. This creates a dangerous privilege escalation path. By failing to contain permissions within their intended scope, the flaw allows excessive access to spread throughout the application environment. An attacker who gains control of the lower-privileged component can then inherit and abuse these unintended permissions, potentially taking full control of the system or accessing restricted data.
Impact réel

Real-world CVEs caused by CWE-271

  • CVE-2000-1213

    Program does not drop privileges after acquiring the raw socket.

  • CVE-2001-0559

    Setuid program does not drop privileges after a parsing error occurs, then calls another program to handle the error.

  • CVE-2001-0787

    Does not drop privileges in related groups when lowering privileges.

  • CVE-2002-0080

    Does not drop privileges in related groups when lowering privileges.

  • CVE-2001-1029

    Does not drop privileges before determining access to certain files.

  • CVE-1999-0813

    Finger daemon does not drop privileges when executing programs on behalf of the user being fingered.

  • CVE-1999-1326

    FTP server does not drop privileges if a connection is aborted during file transfer.

  • CVE-2000-0172

    Program only uses seteuid to drop privileges.

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 C

The following code calls chroot() to restrict the application to a subset of the filesystem below APP_HOME in order to prevent an attacker from using the program to gain unauthorized access to files located elsewhere. The code then opens a file specified by the user and processes the contents of the file.

Vulnérable C 
chroot(APP_HOME);
  chdir("/");
  FILE* data = fopen(argv[1], "r+");
  ...
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-271

  • Architecture and Design Compartmentalize the system to have "safe" areas where trust boundaries can be unambiguously drawn. Do not allow sensitive data to go outside of the trust boundary and always be careful when interfacing with a compartment outside of the safe area. Ensure that appropriate compartmentalization is built into the system design, and the compartmentalization allows for and reinforces privilege separation functionality. Architects and designers should rely on the principle of least privilege to decide the appropriate time to use privileges and the time to drop privileges.
  • Architecture and Design / Operation Very carefully manage the setting, management, and handling of privileges. Explicitly manage trust zones in the software.
  • Architecture and Design Consider following the principle of separation of privilege. Require multiple conditions to be met before permitting access to a system resource.
Signaux de détection

How to detect CWE-271

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-271 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-271 ?

This vulnerability occurs when a system or process fails to reduce its elevated permissions before transferring control of a resource to a less-privileged user or component.

Quelle est la gravité de CWE-271 ?

MITRE évalue la probabilité d'exploitation comme Élevée — cette faiblesse est activement exploitée et doit être priorisée pour la remédiation.

Quels langages ou plateformes sont affectés par CWE-271 ?

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-271 ?

Compartmentalize the system to have "safe" areas where trust boundaries can be unambiguously drawn. Do not allow sensitive data to go outside of the trust boundary and always be careful when interfacing with a compartment outside of the safe area. Ensure that appropriate compartmentalization is built into the system design, and the compartmentalization allows for and reinforces privilege separation functionality. Architects and designers should rely on the principle of least privilege to…

Comment Plexicus détecte et corrige CWE-271 ?

Le moteur SAST de Plexicus reconnaît la signature de flux de données de CWE-271 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-271 ?

MITRE publie la définition canonique à https://cwe.mitre.org/data/definitions/271.html. Vous pouvez également consulter la documentation OWASP et NIST pour des conseils adjacents.

Faiblesses associées

Weaknesses related to CWE-271

CWE-269 Parent

Improper Privilege Management

This vulnerability occurs when an application fails to correctly manage user permissions, allowing someone to perform actions or access…

CWE-250 Frère

Execution with Unnecessary Privileges

This vulnerability occurs when software runs with higher permissions than it actually needs to perform its tasks. This excessive privilege…

CWE-266 Frère

Incorrect Privilege Assignment

This vulnerability occurs when a system mistakenly grants a user, process, or entity a specific permission or privilege they should not…

CWE-267 Frère

Privilege Defined With Unsafe Actions

This vulnerability occurs when a system grants a user, role, or process a specific permission that can be misused to perform dangerous,…

CWE-268 Frère

Privilege Chaining

Privilege chaining occurs when an attacker combines two separate permissions or capabilities, neither of which is dangerous on its own, to…

CWE-270 Frère

Privilege Context Switching Error

This vulnerability occurs when an application fails to properly manage user permissions while moving between different security contexts,…

CWE-274 Frère

Improper Handling of Insufficient Privileges

This vulnerability occurs when an application fails to properly manage situations where it lacks the necessary permissions to execute an…

CWE-648 Frère

Incorrect Use of Privileged APIs

This vulnerability occurs when software incorrectly uses functions that require special permissions. Attackers can exploit these mistakes…

CWE-272 Enfant

Least Privilege Violation

This vulnerability occurs when software fails to reduce its elevated system privileges after completing a sensitive operation, leaving it…

Ressources

Further reading

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