CWE-91 Base Borrador

XML Injection (aka Blind XPath Injection)

XML Injection occurs when an application fails to properly validate or escape user-controlled input before including it in XML documents or queries. This allows attackers to inject malicious XML…

Definición

What is CWE-91?

XML Injection occurs when an application fails to properly validate or escape user-controlled input before including it in XML documents or queries. This allows attackers to inject malicious XML elements or syntax, potentially altering the document's structure, extracting sensitive data, or disrupting processing logic.

XML documents use special characters like <, >, &, and " to define elements and attributes. If user input containing these characters is inserted without neutralization, an attacker can break out of intended data fields and inject new XML tags, modify queries (like XPath), or even reference external entities. This can lead to data theft, logic bypasses, or denial of service. Preventing XML injection requires strict input validation, context-aware output encoding, and the use of parameterized XPath interfaces. Managing this at scale across numerous codebases and APIs is difficult; an ASPM platform like Plexicus can help you track and remediate these flaws across your entire stack by correlating SAST findings with runtime behavior and prioritizing the most critical exposures.

Impacto en el mundo real

Real-world CVEs caused by CWE-91

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
Identifica una ruta de código que maneje entrada no confiable sin validación.
2
Crea un payload que ejercite el comportamiento inseguro — inyección, traversal, overflow o abuso de lógica.
3
Envía el payload a través de una solicitud normal y observa la reacción de la aplicación.
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-91

Implementation Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does. When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue." Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.

Señales de detección

How to detect CWE-91

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-91

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

Plexicus turns CWE catalogs into evidence: every CWE-pattern is matched against your real code graph, reach is proven on a sandbox clone, and verified findings ship as reviewed PRs.

Request AI Swarm Pentest

Preguntas frecuentes

Frequently asked questions

¿Qué es CWE-91?

¿Qué gravedad tiene CWE-91?

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-91?

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

¿Cómo puedo prevenir CWE-91?

Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does. When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and…

¿Cómo detecta y corrige Plexicus CWE-91?

El motor SAST de Plexicus detecta la firma de flujo de datos para CWE-91 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-91?

MITRE publica la definición canónica en https://cwe.mitre.org/data/definitions/91.html. También puedes consultar la documentación de OWASP y NIST para guías relacionadas.

Debilidades relacionadas

Weaknesses related to CWE-91

CWE-74 Padre

Listo para validar lo que importa.

Plexicus es Proof-Driven AppSec: hallazgos validados, comprensión contextual y remediación revisada — anclada en evidencia, acotada contigo.

Reservar Pentest

XML Injection (aka Blind XPath Injection)

What is CWE-91?

Real-world CVEs caused by CWE-91

Ruta del atacante paso a paso

Vulnerable pseudo

Secure pseudo

How to prevent CWE-91

How to detect CWE-91

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

Frequently asked questions

Weaknesses related to CWE-91

Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')

Improper Neutralization of Formula Elements in a CSV File

Failure to Sanitize Special Elements into a Different Plane (Special Element Injection)

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

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

Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Improper Neutralization of Argument Delimiters in a Command ('Argument Injection')

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

Improper Neutralization of Special Elements used in an Expression Language Statement ('Expression Language Injection')

Further reading

Listo para validar lo que importa.

Comprueba si el AI Swarm Pentest encaja en tu entorno.

Solicitud recibida. Reserva el siguiente paso.

Sample evidence handover

Server-Side Request Forgery in `webhooks/receiver`