CWE-611: Improper Restriction of XML External Entity Reference

Définition

What is CWE-611?

This vulnerability occurs when an application processes XML input without properly restricting external entity references. Attackers can exploit this to read local files, trigger internal network requests, or cause denial of service.

XML parsers often support Document Type Definitions (DTDs), which can define custom entities. When these entities point to external URIs (like file://, http://), the parser may fetch and include that external content. An attacker can inject a malicious DTD that references sensitive system files (e.g., /etc/passwd, C:\Windows\win.ini) or internal endpoints, leading to data exposure or server-side request forgery (SSRF). The retrieved data is often reflected in the application's output, such as error messages or API responses. Preventing XXE requires disabling DTD processing entirely or securely configuring the XML parser to reject external entities. Since manual code reviews and traditional SAST tools can miss parser configurations, managing this at scale is difficult; an ASPM like Plexicus can help you track and remediate these flaws across your entire stack by correlating findings with actual runtime behavior and suggesting prioritized fixes.

Impact réel

Real-world CVEs caused by CWE-611

CVE-2022-42745

Recruiter software allows reading arbitrary files using XXE
CVE-2005-1306

A browser control can allow remote attackers to determine the existence of files via Javascript containing XML script.
CVE-2012-5656

XXE during SVG image conversion
CVE-2012-2239

XXE in PHP application allows reading the application's configuration file.
CVE-2012-3489

XXE in database server
CVE-2012-4399

XXE in rapid web application development framework allows reading arbitrary files.
CVE-2012-3363

XXE via XML-RPC request.
CVE-2012-0037

XXE in office document product using RDF.

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-611

Implementation / System Configuration Many XML parsers and validators can be configured to disable external entity expansion.

Signaux de détection

How to detect CWE-611

Automated Static Analysis High

Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc.)

CWE-611

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Questions fréquentes

Frequently asked questions

Qu'est-ce que CWE-611 ?

This vulnerability occurs when an application processes XML input without properly restricting external entity references. Attackers can exploit this to read local files, trigger internal network requests, or cause denial of service.

Quelle est la gravité de CWE-611 ?

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-611 ?

MITRE lists the following affected platforms: XML, Web Based.

Comment puis-je prévenir CWE-611 ?

Many XML parsers and validators can be configured to disable external entity expansion.

Comment Plexicus détecte et corrige CWE-611 ?

Le moteur SAST de Plexicus reconnaît la signature de flux de données de CWE-611 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-611 ?

MITRE publie la définition canonique à https://cwe.mitre.org/data/definitions/611.html. Vous pouvez également consulter la documentation OWASP et NIST pour des conseils adjacents.

Faiblesses associées

Weaknesses related to CWE-611

CWE-610 Parent

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Improper Restriction of XML External Entity Reference

What is CWE-611?

Real-world CVEs caused by CWE-611

Parcours de l'attaquant étape par étape

Vulnerable pseudo

Secure pseudo

How to prevent CWE-611

How to detect CWE-611

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

Frequently asked questions

Weaknesses related to CWE-611

Externally Controlled Reference to a Resource in Another Sphere

Improper Restriction of Rendered UI Layers or Frames

External Control of System or Configuration Setting

Session Fixation

Unintended Proxy or Intermediary ('Confused Deputy')

Use of Externally-Controlled Input to Select Classes or Code ('Unsafe Reflection')

URL Redirection to Untrusted Site ('Open Redirect')

External Control of File Name or Path

Server-Side Request Forgery (SSRF)

Further reading

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Sample evidence handover

Server-Side Request Forgery in `webhooks/receiver`