CWE-348 Base Borrador

Use of Less Trusted Source

This vulnerability occurs when a system has access to multiple sources for the same critical data, but it chooses to rely on the less secure or less trustworthy one. This creates a security gap…

Definición

What is CWE-348?

This vulnerability occurs when a system has access to multiple sources for the same critical data, but it chooses to rely on the less secure or less trustworthy one. This creates a security gap because the system ignores better-protected alternatives that offer stronger verification or are harder for attackers to compromise.

Think of this flaw as a developer choosing to trust a rumor from an anonymous tip line over an official, signed document from a verified authority—even though both claim to state the same fact. The core issue isn't about missing data, but about making a poor choice between available sources. This often happens in code that fetches configuration, license keys, or critical parameters from multiple locations (like a local file, a network service, and a hardware security module) but defaults to the most convenient, rather than the most secure, option. To prevent this, your code should implement a clear trust hierarchy. Always design your system to prefer and require the most authoritative source—the one with the strongest cryptographic verification, integrity checks, or tamper resistance. This means explicitly validating the source before trusting its data and failing securely if the high-trust source is unavailable, rather than silently falling back to a weaker alternative that an attacker could easily manipulate.

Impacto en el mundo real

Real-world CVEs caused by CWE-348

CVE-2001-0860

Product uses IP address provided by a client, instead of obtaining it from the packet headers, allowing easier spoofing.
CVE-2004-1950

Web product uses the IP address in the X-Forwarded-For HTTP header instead of a server variable that uses the connecting IP address, allowing filter bypass.
CVE-2001-0908

Product logs IP address specified by the client instead of obtaining it from the packet headers, allowing information hiding.
CVE-2006-1126

PHP application uses IP address from X-Forwarded-For HTTP header, instead of REMOTE_ADDR.

Cómo lo explotan los atacantes

Ruta del atacante paso a paso

1
This code attempts to limit the access of a page to certain IP Addresses. It checks the 'HTTP_X_FORWARDED_FOR' header in case an authorized user is sending the request through a proxy.
2
The 'HTTP_X_FORWARDED_FOR' header can be user controlled and so should never be trusted. An attacker can falsify the header to gain access to the page.
3
This fixed code only trusts the 'REMOTE_ADDR' header and so avoids the issue:
4
Be aware that 'REMOTE_ADDR' can still be spoofed. This may seem useless because the server will send the response to the fake address and not the attacker, but this may still be enough to conduct an attack. For example, if the generatePage() function in this code is resource intensive, an attacker could flood the server with fake requests using an authorized IP and consume significant resources. This could be a serious DoS attack even though the attacker would never see the page's sensitive content.

Ejemplo de código vulnerable

Vulnerable PHP

This code attempts to limit the access of a page to certain IP Addresses. It checks the 'HTTP_X_FORWARDED_FOR' header in case an authorized user is sending the request through a proxy.

Vulnerable PHP

$requestingIP = '0.0.0.0';
  if (array_key_exists('HTTP_X_FORWARDED_FOR', $_SERVER)) {
  	$requestingIP = $_SERVER['HTTP_X_FORWARDED_FOR'];
  else{
  	$requestingIP = $_SERVER['REMOTE_ADDR'];
  }
  if(in_array($requestingIP,$ipAllowlist)){
  	generatePage();
  	return;
  }
  else{
  	echo "You are not authorized to view this page";
  	return;
  }

Ejemplo de código seguro

Secure PHP

This fixed code only trusts the 'REMOTE_ADDR' header and so avoids the issue:

Seguro PHP

$requestingIP = '0.0.0.0';
  if (array_key_exists('HTTP_X_FORWARDED_FOR', $_SERVER)) {
  	echo "This application cannot be accessed through a proxy.";
  	return;
  else{
  	$requestingIP = $_SERVER['REMOTE_ADDR'];
  }
```
...*

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-348

Architecture Use safe-by-default frameworks and APIs that prevent the unsafe pattern from being expressible.
Implementation Validate input at trust boundaries; use allowlists, not denylists.
Implementation Apply the principle of least privilege to credentials, file paths, and runtime permissions.
Testing Cover this weakness in CI: SAST rules + targeted unit tests for the data flow.
Operation Monitor logs for the runtime signals listed in the next section.

Señales de detección

How to detect CWE-348

SAST High

Ejecuta análisis estático (SAST) sobre el código buscando el patrón inseguro en el flujo de datos.

DAST Moderate

Ejecuta pruebas dinámicas de seguridad de aplicaciones (DAST) contra el endpoint en vivo.

Runtime Moderate

Vigila los logs en tiempo de ejecución para detectar trazas de excepción inusuales, entradas malformadas o intentos de bypass de autorización.

Code review Moderate

Revisión de código: marca cualquier código nuevo que maneje entrada desde esta superficie sin usar los helpers validados del framework.

CWE-348

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Preguntas frecuentes

Frequently asked questions

¿Qué es CWE-348?

¿Qué gravedad tiene CWE-348?

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-348?

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

¿Cómo puedo prevenir CWE-348?

Use safe-by-default frameworks, validate untrusted input at trust boundaries, and apply the principle of least privilege. Cover the data-flow signature in CI with SAST.

¿Cómo detecta y corrige Plexicus CWE-348?

El motor SAST de Plexicus detecta la firma de flujo de datos para CWE-348 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-348?

MITRE publica la definición canónica en https://cwe.mitre.org/data/definitions/348.html. También puedes consultar la documentación de OWASP y NIST para guías relacionadas.

Debilidades relacionadas

Weaknesses related to CWE-348

CWE-345 Padre

Listo para validar lo que importa.

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Reservar Pentest

Use of Less Trusted Source

What is CWE-348?

Real-world CVEs caused by CWE-348

Ruta del atacante paso a paso

Vulnerable PHP

Secure PHP

How to prevent CWE-348

How to detect CWE-348

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

Frequently asked questions

Weaknesses related to CWE-348

Insufficient Verification of Data Authenticity

Missing Source Correlation of Multiple Independent Data

Origin Validation Error

Improper Verification of Cryptographic Signature

Acceptance of Extraneous Untrusted Data With Trusted Data

Insufficient Type Distinction

Cross-Site Request Forgery (CSRF)

Missing Support for Integrity Check

Improper Validation of Integrity Check Value

Further reading

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Sample evidence handover

Server-Side Request Forgery in `webhooks/receiver`