Ejecuta análisis estático (SAST) sobre el código buscando el patrón inseguro en el flujo de datos.
CWE-636 Clase Borrador
Not Failing Securely ('Failing Open')
This vulnerability occurs when a system, upon encountering an error or failure, defaults to its least secure configuration instead of a safer alternative. Examples include reverting to the weakest…
Definición
What is CWE-636?
This vulnerability occurs when a system, upon encountering an error or failure, defaults to its least secure configuration instead of a safer alternative. Examples include reverting to the weakest encryption or the most permissive access rules.
Failing open creates a dangerous gap where the system operates with known, weaker security controls. This directly introduces the vulnerabilities associated with that permissive state, making it significantly easier for an attacker to exploit the system. Often, this design choice is made to prioritize uptime and reduce support overhead, mistakenly valuing continuous functionality over security.
This approach fundamentally undermines security posture and provides administrators with a false sense of protection. The secure alternative is to "fail closed" or "fail safe," where the system denies access or stops operations until the issue can be safely resolved, ensuring security is never automatically compromised for convenience.
Impacto en el mundo real
Real-world CVEs caused by CWE-636
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The failure of connection attempts in a web browser resets DNS pin restrictions. An attacker can then bypass the same origin policy by rebinding a domain name to a different IP address. This was an attempt to "fail functional."
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Incorrect prioritization leads to the selection of a weaker cipher. Although it is not known whether this issue occurred in implementation or design, it is feasible that a poorly designed algorithm could be a factor.
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.
// 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
// 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-636
- Architecture and Design Subdivide and allocate resources and components so that a failure in one part does not affect the entire product.
Señales de detección
How to detect CWE-636
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.
CWE-636
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.
Preguntas frecuentes ¿Qué es CWE-636?
¿Qué gravedad tiene CWE-636?
¿Qué lenguajes o plataformas se ven afectados por CWE-636?
¿Cómo puedo prevenir CWE-636?
¿Cómo detecta y corrige Plexicus CWE-636?
¿Dónde puedo aprender más sobre CWE-636?
Frequently asked questions
¿Qué es CWE-636?
This vulnerability occurs when a system, upon encountering an error or failure, defaults to its least secure configuration instead of a safer alternative. Examples include reverting to the weakest encryption or the most permissive access rules.
¿Qué gravedad tiene CWE-636?
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-636?
MITRE lists the following affected platforms: Not Technology-Specific, ICS/OT.
¿Cómo puedo prevenir CWE-636?
Subdivide and allocate resources and components so that a failure in one part does not affect the entire product.
¿Cómo detecta y corrige Plexicus CWE-636?
El motor SAST de Plexicus detecta la firma de flujo de datos para CWE-636 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-636?
MITRE publica la definición canónica en https://cwe.mitre.org/data/definitions/636.html. También puedes consultar la documentación de OWASP y NIST para guías relacionadas.
Debilidades relacionadas
Weaknesses related to CWE-636
CWE-657 Padre
Violation of Secure Design Principles
This weakness occurs when a system's architecture or design fails to follow fundamental security principles, creating a flawed foundation…
CWE-1192 Hermano
Improper Identifier for IP Block used in System-On-Chip (SOC)
This weakness occurs when a System-on-Chip (SoC) lacks a secure, unique, and permanent identifier for its internal hardware components (IP…
CWE-1395 Hermano
Dependency on Vulnerable Third-Party Component
This vulnerability occurs when your software relies on an external library, framework, or module that contains known security flaws.
CWE-250 Hermano
Execution with Unnecessary Privileges
This vulnerability occurs when software runs with higher permissions than it actually needs to perform its tasks. This excessive privilege…
CWE-637 Hermano
Unnecessary Complexity in Protection Mechanism (Not Using 'Economy of Mechanism')
This weakness occurs when a security feature is implemented with excessive complexity, creating unnecessary risk. Overly intricate…
CWE-638 Hermano
Not Using Complete Mediation
This vulnerability occurs when software fails to verify access permissions every single time a user or process tries to use a resource.…
CWE-653 Hermano
Improper Isolation or Compartmentalization
This vulnerability occurs when an application fails to enforce strong boundaries between components that operate at different security…
CWE-654 Hermano
Reliance on a Single Factor in a Security Decision
This vulnerability occurs when a system's security check depends almost entirely on just one condition, object, or piece of data to decide…
CWE-655 Hermano
Insufficient Psychological Acceptability
This weakness occurs when security features are so cumbersome or confusing that well-intentioned users feel forced to turn them off or…
Recursos
Further reading
- MITRE — CWE-636 oficial https://cwe.mitre.org/data/definitions/636.html
- The Protection of Information in Computer Systems http://web.mit.edu/Saltzer/www/publications/protection/
- Failing Securely https://web.archive.org/web/20221017053210/https://www.cisa.gov/uscert/bsi/articles/knowledge/principles/failing-securely
¿Listo para validar lo que importa?
Listo para validar lo que importa.
Plexicus es Proof-Driven AppSec: hallazgos validados, comprensión contextual y remediación revisada — anclada en evidencia, acotada contigo.