CWE-611 Base Rascunho

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…

Definição

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 no 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.

Como os atacantes a exploram

Trajeto do atacante passo a passo

  1. 1

    Identificar um caminho de código que trata input não confiável sem validação.

  2. 2

    Criar um payload que explora o comportamento inseguro — injeção, traversal, overflow ou abuso de lógica.

  3. 3

    Entregar o payload através de um pedido normal e observar a reação da aplicação.

  4. 4

    Iterar até que a resposta exponha dados, execute código do atacante ou escale privilégios.

Exemplo de código vulnerável

Vulnerable pseudo

A MITRE não publicou um exemplo de código para este CWE. O padrão abaixo é ilustrativo — consulte os Recursos para referências canónicas.

Vulnerável pseudo 
// Example pattern — see MITRE for the canonical references.
function handleRequest(input) {
  // Untrusted input flows directly into the sensitive sink.
  return executeUnsafe(input);
}
Exemplo 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 verificação de prevenção

How to prevent CWE-611

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

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.)

Correção automática do Plexicus

O Plexicus deteta automaticamente o CWE-611 e abre um PR de correção em menos de 60 segundos.

O Codex Remedium analisa cada commit, identifica esta fraqueza exata e entrega um pull request pronto para revisão com o patch. Sem tickets. Sem transferências.

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Perguntas frequentes

Frequently asked questions

O que é o 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.

Qual a gravidade do CWE-611?

A MITRE não publicou uma classificação de probabilidade de exploração para esta fraqueza. Trate-a como impacto médio até o seu modelo de ameaças provar o contrário.

Que linguagens ou plataformas são afetadas pelo CWE-611?

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

Como posso prevenir o CWE-611?

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

Como é que o Plexicus deteta e corrige o CWE-611?

O motor SAST do Plexicus correlaciona a assinatura de fluxo de dados do CWE-611 em cada commit. Quando é encontrada uma correspondência, o nosso agente Codex Remedium abre um PR de correção com o código corrigido, testes e um resumo de uma linha para o revisor.

Onde posso saber mais sobre o CWE-611?

A MITRE publica a definição canónica em https://cwe.mitre.org/data/definitions/611.html. Pode também consultar a documentação da OWASP e do NIST para orientações adjacentes.

Fraquezas relacionadas

Weaknesses related to CWE-611

CWE-610 Pai

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 Irmão

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 Irmão

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 Irmão

Session Fixation

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

CWE-441 Irmão

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 Irmão

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 Irmão

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 Irmão

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 Irmão

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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