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.

Definición

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 en el mundo real

Real-world CVEs caused by CWE-643

Todavía no hay CVEs públicos enlazados a esta CWE en el catálogo de MITRE.

Cómo lo explotan los atacantes

Ruta del atacante paso a paso

  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.

Ejemplo de código vulnerable

Vulnerable Java

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

Vulnerable 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 del 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 del atacante 
//users/user[login/text()='john' or ''='' and password/text() = '' or ''='']/home_dir/text()
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-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.
Señales de detección

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.)

Auto-corrección de Plexicus

Plexicus detecta automáticamente CWE-643 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-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.

¿Qué gravedad tiene CWE-643?

MITRE califica la probabilidad de explotación como Alta — esta debilidad se explota activamente en la práctica y debe priorizarse para su remediación.

¿Qué lenguajes o plataformas se ven afectados por CWE-643?

MITRE no ha especificado plataformas afectadas para esta CWE — puede aplicar a la mayoría de los stacks de aplicaciones.

¿Cómo puedo prevenir 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.

¿Cómo detecta y corrige Plexicus CWE-643?

El motor SAST de Plexicus detecta la firma de flujo de datos para CWE-643 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-643?

MITRE publica la definición canónica en https://cwe.mitre.org/data/definitions/643.html. También puedes consultar la documentación de OWASP y NIST para guías relacionadas.

Debilidades relacionadas

Weaknesses related to CWE-643

CWE-943 Padre

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 Hermano

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 Hermano

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 Hermano

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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