Ejecuta análisis estático (SAST) sobre el código buscando el patrón inseguro en el flujo de datos.
CWE-420 Base Borrador
Unprotected Alternate Channel
This vulnerability occurs when an application secures its main communication path but leaves a backup or alternative channel with weaker or no protection.
Definición
What is CWE-420?
This vulnerability occurs when an application secures its main communication path but leaves a backup or alternative channel with weaker or no protection.
Think of an application that uses strong encryption for its primary web login but sends password reset codes via unencrypted SMS. An attacker can ignore the fortified main door and easily intercept data through this neglected side channel. This creates a false sense of security, as the overall system is only as strong as its weakest point. Developers often focus all their security efforts on the obvious primary path, forgetting that attackers actively seek out these alternate, less-guarded routes.
To prevent this, you must perform a thorough threat model that maps all data flows, not just the primary ones. Apply consistent security controls—like encryption, authentication, and integrity checks—across every channel that handles sensitive data or critical commands. Regularly test both primary and alternate paths during security assessments to ensure your defenses are uniform and comprehensive.
Impacto en el mundo real
Real-world CVEs caused by CWE-420
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When the internal flash is protected by blocking access on the Data Bus (DBUS), it can still be indirectly accessed through the Instruction Bus (IBUS).
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DB server assumes that local clients have performed authentication, allowing attacker to directly connect to a process to load libraries and execute commands; a socket interface also exists (another alternate channel), so attack can be remote.
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Product does not restrict access to underlying database, so attacker can bypass restrictions by directly querying the database.
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User can avoid lockouts by using an API instead of the GUI to conduct brute force password guessing.
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FTP service can not be disabled even when other access controls would require it.
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Windows named pipe created without authentication/access control, allowing configuration modification.
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Router management interface spawns a separate TCP connection after authentication, allowing hijacking by attacker coming from the same IP address.
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 Verilog
assign addr_auth = (address == 32'hF00) ? 1: 0; Ejemplo de código seguro
Secure Verilog
The bugged line of code is repeated in the Bad example above. The weakness arises from the fact that the SECURE_ME register can be modified by writing to the shadow register COPY_OF_SECURE_ME. The address of COPY_OF_SECURE_ME should also be included in the check. That buggy line of code should instead be replaced as shown in the Good Code Snippet below.
assign addr_auth = (address == 32'hF00 || address == 32'h800F00) ? 1: 0; 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-420
- Architecture and Design Identify all alternate channels and use the same protection mechanisms that are used for the primary channels.
Señales de detección
How to detect CWE-420
Ejecuta pruebas dinámicas de seguridad de aplicaciones (DAST) contra el endpoint en vivo.
Vigila los logs en tiempo de ejecución para detectar trazas de excepción inusuales, entradas malformadas o intentos de bypass de autorización.
Revisión de código: marca cualquier código nuevo que maneje entrada desde esta superficie sin usar los helpers validados del framework.
Plexicus detecta automáticamente CWE-420 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-420?
¿Qué gravedad tiene CWE-420?
¿Qué lenguajes o plataformas se ven afectados por CWE-420?
¿Cómo puedo prevenir CWE-420?
¿Cómo detecta y corrige Plexicus CWE-420?
¿Dónde puedo aprender más sobre CWE-420?
Frequently asked questions
¿Qué es CWE-420?
This vulnerability occurs when an application secures its main communication path but leaves a backup or alternative channel with weaker or no protection.
¿Qué gravedad tiene CWE-420?
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-420?
MITRE no ha especificado plataformas afectadas para esta CWE — puede aplicar a la mayoría de los stacks de aplicaciones.
¿Cómo puedo prevenir CWE-420?
Identify all alternate channels and use the same protection mechanisms that are used for the primary channels.
¿Cómo detecta y corrige Plexicus CWE-420?
El motor SAST de Plexicus detecta la firma de flujo de datos para CWE-420 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-420?
MITRE publica la definición canónica en https://cwe.mitre.org/data/definitions/420.html. También puedes consultar la documentación de OWASP y NIST para guías relacionadas.
Debilidades relacionadas
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