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-104 Variante Borrador
Struts: Form Bean Does Not Extend Validation Class
This vulnerability occurs in Apache Struts applications when a form bean class does not properly extend the framework's validation class. This bypasses the built-in Validator framework, leaving the…
Definición
What is CWE-104?
This vulnerability occurs in Apache Struts applications when a form bean class does not properly extend the framework's validation class. This bypasses the built-in Validator framework, leaving the application without structured input validation and open to various injection and data manipulation attacks.
In Struts, the Validator framework provides a centralized, declarative way to validate user input across forms. When a developer creates a form bean that doesn't extend `ActionForm` (or its Validator subclass), the application misses out on this essential security layer. Instead, input checks become ad-hoc, inconsistent, or entirely absent, making every data field a potential entry point for malicious data.
To prevent this, always ensure your form beans inherit from the appropriate validation-enabled class, such as `ValidatorForm`. This enforces validation rules defined in your `validation.xml` configuration file, ensuring all user input is cleaned and checked before processing. Consistently using the framework's validation mechanism is far more reliable and secure than attempting to manually validate each input throughout your codebase.
Impacto en el mundo real
Real-world CVEs caused by CWE-104
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
In the following Java example the class RegistrationForm is a Struts framework ActionForm Bean that will maintain user information from a registration webpage for an online business site. The user will enter registration data and through the Struts framework the RegistrationForm bean will maintain the user data.
- 2
However, the RegistrationForm class extends the Struts ActionForm class which does not allow the RegistrationForm class to use the Struts validator capabilities. When using the Struts framework to maintain user data in an ActionForm Bean, the class should always extend one of the validator classes, ValidatorForm, ValidatorActionForm, DynaValidatorForm or DynaValidatorActionForm. These validator classes provide default validation and the validate method for custom validation for the Bean object to use for validating input data. The following Java example shows the RegistrationForm class extending the ValidatorForm class and implementing the validate method for validating input data.
- 3
Note that the ValidatorForm class itself extends the ActionForm class within the Struts framework API.
Ejemplo de código vulnerable
Vulnerable Java
In the following Java example the class RegistrationForm is a Struts framework ActionForm Bean that will maintain user information from a registration webpage for an online business site. The user will enter registration data and through the Struts framework the RegistrationForm bean will maintain the user data.
public class RegistrationForm extends org.apache.struts.action.ActionForm {
// private variables for registration form
private String name;
private String email;
...
public RegistrationForm() {
super();
}
// getter and setter methods for private variables
...
} Ejemplo de código seguro
Secure Java
However, the RegistrationForm class extends the Struts ActionForm class which does not allow the RegistrationForm class to use the Struts validator capabilities. When using the Struts framework to maintain user data in an ActionForm Bean, the class should always extend one of the validator classes, ValidatorForm, ValidatorActionForm, DynaValidatorForm or DynaValidatorActionForm. These validator classes provide default validation and the validate method for custom validation for the Bean object to use for validating input data. The following Java example shows the RegistrationForm class extending the ValidatorForm class and implementing the validate method for validating input data.
public class RegistrationForm extends org.apache.struts.validator.ValidatorForm {
// private variables for registration form
private String name;
private String email;
...
public RegistrationForm() {
super();
}
public ActionErrors validate(ActionMapping mapping, HttpServletRequest request) {...}
// getter and setter methods for private variables
...
} 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-104
- Implementation Ensure that all forms extend one of the Validation Classes.
Señales de detección
How to detect CWE-104
Plexicus detecta automáticamente CWE-104 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-104?
¿Qué gravedad tiene CWE-104?
¿Qué lenguajes o plataformas se ven afectados por CWE-104?
¿Cómo puedo prevenir CWE-104?
¿Cómo detecta y corrige Plexicus CWE-104?
¿Dónde puedo aprender más sobre CWE-104?
Frequently asked questions
¿Qué es CWE-104?
This vulnerability occurs in Apache Struts applications when a form bean class does not properly extend the framework's validation class. This bypasses the built-in Validator framework, leaving the application without structured input validation and open to various injection and data manipulation attacks.
¿Qué gravedad tiene CWE-104?
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-104?
MITRE lists the following affected platforms: Java.
¿Cómo puedo prevenir CWE-104?
Ensure that all forms extend one of the Validation Classes.
¿Cómo detecta y corrige Plexicus CWE-104?
El motor SAST de Plexicus detecta la firma de flujo de datos para CWE-104 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-104?
MITRE publica la definición canónica en https://cwe.mitre.org/data/definitions/104.html. También puedes consultar la documentación de OWASP y NIST para guías relacionadas.
Debilidades relacionadas
Weaknesses related to CWE-104
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CWE-243 Hermano
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CWE-253 Hermano
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CWE-296 Hermano
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CWE-304 Hermano
Missing Critical Step in Authentication
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CWE-325 Hermano
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CWE-329 Hermano
Generation of Predictable IV with CBC Mode
This vulnerability occurs when software uses a predictable or reused Initialization Vector (IV) with Cipher Block Chaining (CBC) mode…
CWE-358 Hermano
Improperly Implemented Security Check for Standard
This vulnerability occurs when software fails to correctly implement one or more critical security checks required by a standard protocol,…
Recursos
Further reading
- MITRE — CWE-104 oficial https://cwe.mitre.org/data/definitions/104.html
- Seven Pernicious Kingdoms: A Taxonomy of Software Security Errors https://samate.nist.gov/SSATTM_Content/papers/Seven%20Pernicious%20Kingdoms%20-%20Taxonomy%20of%20Sw%20Security%20Errors%20-%20Tsipenyuk%20-%20Chess%20-%20McGraw.pdf
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