CWE-1386: Insecure Operation on Windows Junction / Mount Point

Définition

What is CWE-1386?

This vulnerability occurs when a Windows application opens a file or directory without properly validating that the path is not a symbolic link (junction or mount point) pointing to a location outside the application's intended security boundary.

On Windows NTFS file systems, junction points and mount points are types of symbolic links (reparse points) that can redirect file operations from one directory to another, potentially to a completely different drive or privileged location. If an application with elevated privileges opens a file without checking for these links, an attacker can replace the expected file with a link to a sensitive system file, registry key, or named object, tricking the application into performing unauthorized read, write, or delete operations. This allows privilege escalation or data manipulation because the privileged process unknowingly operates on the attacker's target. For example, an attacker could redirect a file operation to AUTOEXEC.BAT, critical configuration files, or security databases, causing the application to corrupt, expose, or modify sensitive data with its own high-level permissions. Developers must explicitly validate paths and handle reparse points to confine operations within the intended directory scope.

Impact réel

Real-world CVEs caused by CWE-1386

CVE-2021-26426

Privileged service allows attackers to delete unauthorized files using a directory junction, leading to arbitrary code execution as SYSTEM.
CVE-2020-0863

By creating a mount point and hard links, an attacker can abuse a service to allow users arbitrary file read permissions.
CVE-2019-1161

Chain: race condition (CWE-362) in anti-malware product allows deletion of files by creating a junction (CWE-1386) and using hard links during the time window in which a temporary file is created and deleted.
CVE-2014-0568

Escape from sandbox for document reader by using a mountpoint [REF-1264]

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-1386

Architecture and Design When designing software that will have different rights than the executer, the software should check that files that it is interacting with are not improper hard links or mount points. One way to do this in Windows is to use the functionality embedded in the following command: "dir /al /s /b" or, in PowerShell, use LinkType as a filter. In addition, some software uses authentication via signing to ensure that the file is the correct one to use. Make checks atomic with the file action, otherwise a TOCTOU weakness (CWE-367) can be introduced.

Signaux de détection

How to detect CWE-1386

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.

CWE-1386

Don't catalog this weakness. Prove it's reachable.

Plexicus turns CWE catalogs into evidence: every CWE-pattern is matched against your real code graph, reach is proven on a sandbox clone, and verified findings ship as reviewed PRs.

Request AI Swarm Pentest

Questions fréquentes

Frequently asked questions

Qu'est-ce que CWE-1386 ?

This vulnerability occurs when a Windows application opens a file or directory without properly validating that the path is not a symbolic link (junction or mount point) pointing to a location outside the application's intended security boundary.

Quelle est la gravité de CWE-1386 ?

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-1386 ?

MITRE lists the following affected platforms: Windows.

Comment puis-je prévenir CWE-1386 ?

When designing software that will have different rights than the executer, the software should check that files that it is interacting with are not improper hard links or mount points. One way to do this in Windows is to use the functionality embedded in the following command: "dir /al /s /b" or, in PowerShell, use LinkType as a filter. In addition, some software uses authentication via signing to ensure that the file is the correct one to use. Make checks atomic with the file action,…

Comment Plexicus détecte et corrige CWE-1386 ?

Le moteur SAST de Plexicus reconnaît la signature de flux de données de CWE-1386 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-1386 ?

MITRE publie la définition canonique à https://cwe.mitre.org/data/definitions/1386.html. Vous pouvez également consulter la documentation OWASP et NIST pour des conseils adjacents.

Faiblesses associées

Weaknesses related to CWE-1386

CWE-59 Parent

Prêt à valider ce qui compte.

Plexicus est Proof-Driven AppSec : findings validés, compréhension contextuelle et remédiation relue — ancrée dans la preuve, scopée avec vous.

Réserver un Pentest

Insecure Operation on Windows Junction / Mount Point

What is CWE-1386?

Real-world CVEs caused by CWE-1386

Parcours de l'attaquant étape par étape

Vulnerable pseudo

Secure pseudo

How to prevent CWE-1386

How to detect CWE-1386

Don't catalog this weakness. Prove it's reachable.

Frequently asked questions

Weaknesses related to CWE-1386

Improper Link Resolution Before File Access ('Link Following')

UNIX Symbolic Link (Symlink) Following

UNIX Hard Link

Windows Shortcut Following (.LNK)

Windows Hard Link

Further reading

Prêt à valider ce qui compte.

Vérifiez si l'AI Swarm Pentest convient à votre environnement.

Demande reçue. Réservez la prochaine étape.

Sample evidence handover

Server-Side Request Forgery in `webhooks/receiver`