CWE-611 Base Borrador

Improper Restriction of XML External Entity Reference

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…

Definición

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.
Impacto en el mundo real

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.

Cómo lo explotan los atacantes

Ruta del atacante paso a paso

  1. 1

    Identifica una ruta de código que maneje entrada no confiable sin validación.

  2. 2

    Crea un payload que ejercite el comportamiento inseguro — inyección, traversal, overflow o abuso de lógica.

  3. 3

    Envía el payload a través de una solicitud normal y observa la reacción de la aplicación.

  4. 4

    Itera hasta que la respuesta filtre datos, ejecute código del atacante o escale privilegios.

Ejemplo de código vulnerable

Vulnerable pseudo

MITRE no ha publicado un ejemplo de código para esta CWE. El patrón siguiente es ilustrativo — consulta Recursos para referencias canónicas.

Vulnerable pseudo 
// Example pattern — see MITRE for the canonical references.
function handleRequest(input) {
  // Untrusted input flows directly into the sensitive sink.
  return executeUnsafe(input);
}
Ejemplo de código seguro

Secure pseudo

Seguro 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.
Lista de prevención

How to prevent CWE-611

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

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.)

Auto-corrección de Plexicus

Plexicus detecta automáticamente CWE-611 y abre un PR de corrección en menos de 60 segundos.

Codex Remedium escanea cada commit, identifica esta debilidad concreta y entrega un pull request listo para revisión con el parche. Sin tickets. Sin traspasos.

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Preguntas frecuentes

Frequently asked questions

¿Qué es 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.

¿Qué gravedad tiene CWE-611?

MITRE no ha publicado una calificación de probabilidad de explotación para esta debilidad. Trátala como de impacto medio hasta que tu modelo de amenazas demuestre lo contrario.

¿Qué lenguajes o plataformas se ven afectados por CWE-611?

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

¿Cómo puedo prevenir CWE-611?

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

¿Cómo detecta y corrige Plexicus CWE-611?

El motor SAST de Plexicus detecta la firma de flujo de datos para CWE-611 en cada commit. Cuando hay coincidencia, nuestro agente Codex Remedium abre un PR de corrección con el código corregido, las pruebas y un resumen de una línea para el revisor.

¿Dónde puedo aprender más sobre CWE-611?

MITRE publica la definición canónica en https://cwe.mitre.org/data/definitions/611.html. También puedes consultar la documentación de OWASP y NIST para guías relacionadas.

Debilidades relacionadas

Weaknesses related to CWE-611

CWE-610 Padre

Externally Controlled Reference to a Resource in Another Sphere

This vulnerability occurs when an application uses user-supplied input to reference a resource located outside its intended security…

CWE-1021 Hermano

Improper Restriction of Rendered UI Layers or Frames

This vulnerability occurs when a web application fails to properly control whether its pages can be embedded within frames or UI layers…

CWE-15 Hermano

External Control of System or Configuration Setting

This vulnerability occurs when an application allows users to directly modify critical system settings or configuration values from an…

CWE-384 Hermano

Session Fixation

Session fixation occurs when an application authenticates a user without first destroying the previous session ID. This allows an attacker…

CWE-441 Hermano

Unintended Proxy or Intermediary ('Confused Deputy')

A confused deputy vulnerability occurs when a system receives a request from a client and forwards it to an external destination without…

CWE-470 Hermano

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

This vulnerability occurs when an application uses unvalidated external input, like a URL parameter or form field, to dynamically decide…

CWE-601 Hermano

URL Redirection to Untrusted Site ('Open Redirect')

An open redirect vulnerability occurs when a web application uses unvalidated user input to determine the destination of a redirect,…

CWE-73 Hermano

External Control of File Name or Path

This vulnerability occurs when an application uses unvalidated user input to construct file or directory paths for filesystem operations.

CWE-918 Hermano

Server-Side Request Forgery (SSRF)

Server-Side Request Forgery (SSRF) occurs when a web application fetches a remote resource based on user-controlled input, but fails to…

Recursos

Further reading

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