CWE-643 Base Incompleto High likelihood

Improper Neutralization of Data within XPath Expressions ('XPath Injection')

XPath Injection occurs when an application uses unvalidated user input to build an XPath query for an XML database. Without proper sanitization, attackers can manipulate the query's structure.

Definição

What is CWE-643?

XPath Injection occurs when an application uses unvalidated user input to build an XPath query for an XML database. Without proper sanitization, attackers can manipulate the query's structure.
This vulnerability allows an attacker to alter the intended logic of the XPath expression. By injecting special characters or control sequences, they can change which data is retrieved from the XML source, potentially bypassing application logic, authentication, or access controls. Successful exploitation can lead to unauthorized data exposure, information disclosure, or manipulation of application flow. Developers must treat all user input used in XPath queries as untrusted and implement proper validation or parameterization to prevent these attacks.
Impacto no mundo real

Real-world CVEs caused by CWE-643

Ainda não há referências CVE públicas associadas a este CWE no catálogo da MITRE.

Como os atacantes a exploram

Trajeto do atacante passo a passo

  1. 1

    Consider the following simple XML document that stores authentication information and a snippet of Java code that uses XPath query to retrieve authentication information:

  2. 2

    The Java code used to retrieve the home directory based on the provided credentials is:

  3. 3

    Assume that user "john" wishes to leverage XPath Injection and login without a valid password. By providing a username "john" and password "' or ''='" the XPath expression now becomes

  4. 4

    This lets user "john" login without a valid password, thus bypassing authentication.

Exemplo de código vulnerável

Vulnerable Java

The Java code used to retrieve the home directory based on the provided credentials is:

Vulnerável Java 
XPath xpath = XPathFactory.newInstance().newXPath();
  XPathExpression xlogin = xpath.compile("//users/user[login/text()='" + login.getUserName() + "' and password/text() = '" + login.getPassword() + "']/home_dir/text()");
  Document d = DocumentBuilderFactory.newInstance().newDocumentBuilder().parse(new File("db.xml"));
  String homedir = xlogin.evaluate(d);
Payload do atacante

Assume that user "john" wishes to leverage XPath Injection and login without a valid password. By providing a username "john" and password "' or ''='" the XPath expression now becomes

Payload do atacante 
//users/user[login/text()='john' or ''='' and password/text() = '' or ''='']/home_dir/text()
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-643

  • Implementation Use parameterized XPath queries (e.g. using XQuery). This will help ensure separation between data plane and control plane.
  • Implementation Properly validate user input. Reject data where appropriate, filter where appropriate and escape where appropriate. Make sure input that will be used in XPath queries is safe in that context.
Sinais de deteção

How to detect CWE-643

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-643 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-643?

XPath Injection occurs when an application uses unvalidated user input to build an XPath query for an XML database. Without proper sanitization, attackers can manipulate the query's structure.

Qual a gravidade do CWE-643?

A MITRE classifica a probabilidade de exploração como Alta — esta fraqueza é ativamente explorada em campo e deve ser priorizada para remediação.

Que linguagens ou plataformas são afetadas pelo CWE-643?

A MITRE não especificou as plataformas afetadas por este CWE — pode aplicar-se à maioria das stacks de aplicações.

Como posso prevenir o CWE-643?

Use parameterized XPath queries (e.g. using XQuery). This will help ensure separation between data plane and control plane. Properly validate user input. Reject data where appropriate, filter where appropriate and escape where appropriate. Make sure input that will be used in XPath queries is safe in that context.

Como é que o Plexicus deteta e corrige o CWE-643?

O motor SAST do Plexicus correlaciona a assinatura de fluxo de dados do CWE-643 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-643?

A MITRE publica a definição canónica em https://cwe.mitre.org/data/definitions/643.html. Pode também consultar a documentação da OWASP e do NIST para orientações adjacentes.

Fraquezas relacionadas

Weaknesses related to CWE-643

CWE-943 Pai

Improper Neutralization of Special Elements in Data Query Logic

This vulnerability occurs when an application builds a query for a data store (like a database) but fails to properly sanitize…

CWE-652 Irmão

Improper Neutralization of Data within XQuery Expressions ('XQuery Injection')

XQuery Injection occurs when an application uses unvalidated user input to build an XQuery expression for querying an XML database.…

CWE-89 Irmão

Improper Neutralization of Special Elements used in an SQL Command ('SQL Injection')

SQL Injection occurs when an application builds a database query using untrusted user input without properly sanitizing it. This allows an…

CWE-90 Irmão

Improper Neutralization of Special Elements used in an LDAP Query ('LDAP Injection')

This vulnerability occurs when an application builds an LDAP query using untrusted user input without properly sanitizing it. An attacker…

Recursos

Further reading

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