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-441 Clase Borrador
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 properly identifying the original source. This makes the…
Definición
What is CWE-441?
A confused deputy vulnerability occurs when a system receives a request from a client and forwards it to an external destination without properly identifying the original source. This makes the system appear to be the originator of the request, effectively turning it into an unintended proxy for the client.
Attackers exploit this flaw when they cannot reach a target system directly. By sending a malicious request to your vulnerable application, they can have it relayed to the protected target. Since the request now originates from your system's IP address and context, it can bypass network firewalls, IP-based allowlists, and hide the attacker's true location, enabling unauthorized access or actions.
This becomes a critical security issue only under specific conditions: your application must have higher privileges or different network access than the initial requester; the attacker must be blocked from contacting the target directly; and the attacker must be able to craft a request that your application forwards unintentionally. This often involves specifying an unexpected host, port, internal IP, or a restricted command within an otherwise permitted service request.
Impacto en el mundo real
Real-world CVEs caused by CWE-441
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FTP bounce attack. The design of the protocol allows an attacker to modify the PORT command to cause the FTP server to connect to other machines besides the attacker's.
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RPC portmapper could redirect service requests from an attacker to another entity, which thinks the requests came from the portmapper.
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FTP server does not ensure that the IP address in a PORT command is the same as the FTP user's session, allowing port scanning by proxy.
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Web server allows attackers to request a URL from another server, including other ports, which allows proxied scanning.
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CGI script accepts and retrieves incoming URLs.
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Bounce attack allows access to TFTP from trusted side.
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Web-based mail program allows internal network scanning using a modified POP3 port number.
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URL-downloading library automatically follows redirects to file:// and scp:// URLs
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 Other
A SoC contains a microcontroller (running ring-3 (least trusted ring) code), a Memory Mapped Input Output (MMIO) mapped IP core (containing design-house secrets), and a Direct Memory Access (DMA) controller, among several other compute elements and peripherals. The SoC implements access control to protect the registers in the IP core (which registers store the design-house secrets) from malicious, ring-3 (least trusted ring) code executing on the microcontroller. The DMA controller, however, is not blocked off from accessing the IP core for functional reasons.
The code in ring-3 (least trusted ring) of the microcontroller attempts to directly read the protected registers in IP core through MMIO transactions. However, this attempt is blocked due to the implemented access control. Now, the microcontroller configures the DMA core to transfer data from the protected registers to a memory region that it has access to. The DMA core, which is acting as an intermediary in this transaction, does not preserve the identity of the microcontroller and, instead, initiates a new transaction with its own identity. Since the DMA core has access, the transaction (and hence, the attack) is successful. Ejemplo de código seguro
Secure Other
The weakness here is that the intermediary or the proxy agent did not ensure the immutability of the identity of the microcontroller initiating the transaction.
The DMA core forwards this transaction with the identity of the code executing on the microcontroller, which is the original initiator of the end-to-end transaction. Now the transaction is blocked, as a result of forwarding the identity of the true initiator which lacks the permission to access the confidential MMIO mapped IP core. 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-441
- Architecture and Design Enforce the use of strong mutual authentication mechanism between the two parties.
- Architecture and Design Whenever a product is an intermediary or proxy for transactions between two other components, the proxy core should not drop the identity of the initiator of the transaction. The immutability of the identity of the initiator must be maintained and should be forwarded all the way to the target.
Señales de detección
How to detect CWE-441
Plexicus detecta automáticamente CWE-441 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.
Preguntas frecuentes ¿Qué es CWE-441?
¿Qué gravedad tiene CWE-441?
¿Qué lenguajes o plataformas se ven afectados por CWE-441?
¿Cómo puedo prevenir CWE-441?
¿Cómo detecta y corrige Plexicus CWE-441?
¿Dónde puedo aprender más sobre CWE-441?
Frequently asked questions
¿Qué es CWE-441?
A confused deputy vulnerability occurs when a system receives a request from a client and forwards it to an external destination without properly identifying the original source. This makes the system appear to be the originator of the request, effectively turning it into an unintended proxy for the client.
¿Qué gravedad tiene CWE-441?
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-441?
MITRE lists the following affected platforms: Not OS-Specific, Not Architecture-Specific, Not Technology-Specific.
¿Cómo puedo prevenir CWE-441?
Enforce the use of strong mutual authentication mechanism between the two parties. Whenever a product is an intermediary or proxy for transactions between two other components, the proxy core should not drop the identity of the initiator of the transaction. The immutability of the identity of the initiator must be maintained and should be forwarded all the way to the target.
¿Cómo detecta y corrige Plexicus CWE-441?
El motor SAST de Plexicus detecta la firma de flujo de datos para CWE-441 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-441?
MITRE publica la definición canónica en https://cwe.mitre.org/data/definitions/441.html. También puedes consultar la documentación de OWASP y NIST para guías relacionadas.
Debilidades relacionadas
Weaknesses related to CWE-441
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Recursos
Further reading
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