CWE-104 Variante Brouillon

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…

Définition

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.
Impact réel

Real-world CVEs caused by CWE-104

Aucune référence CVE publique n'est liée à ce CWE dans le catalogue MITRE pour le moment.

Comment les attaquants l'exploitent

Parcours de l'attaquant étape par étape

  1. 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. 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. 3

    Note that the ValidatorForm class itself extends the ActionForm class within the Struts framework API.

Exemple de code vulnérable

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.

Vulnérable Java 
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
  		...
  }
Exemple de code sécurisé

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.

Sécurisé Java 
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.
Liste de contrôle de prévention

How to prevent CWE-104

  • Implementation Ensure that all forms extend one of the Validation Classes.
Signaux de détection

How to detect CWE-104

Automated Static Analysis High

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.)

Correction automatique Plexicus

Plexicus détecte automatiquement CWE-104 et ouvre une PR de correction en moins de 60 secondes.

Codex Remedium analyse chaque commit, identifie cette faiblesse précise et livre une pull request prête à être relue avec le correctif. Pas de tickets. Pas de transferts.

Obtenir une démo Essayer Plexicus gratuitement
Questions fréquentes

Frequently asked questions

Qu'est-ce que 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.

Quelle est la gravité de CWE-104 ?

MITRE n'a pas publié de note de probabilité d'exploitation pour cette faiblesse. Traitez-la comme un impact moyen jusqu'à ce que votre modèle de menace prouve le contraire.

Quels langages ou plateformes sont affectés par CWE-104 ?

MITRE lists the following affected platforms: Java.

Comment puis-je prévenir CWE-104 ?

Ensure that all forms extend one of the Validation Classes.

Comment Plexicus détecte et corrige CWE-104 ?

Le moteur SAST de Plexicus reconnaît la signature de flux de données de CWE-104 à chaque commit. Lorsqu'une correspondance est trouvée, notre agent Codex Remedium ouvre une PR de correction avec le code corrigé, les tests et un résumé d'une ligne pour le relecteur.

Où puis-je en savoir plus sur CWE-104 ?

MITRE publie la définition canonique à https://cwe.mitre.org/data/definitions/104.html. Vous pouvez également consulter la documentation OWASP et NIST pour des conseils adjacents.

Faiblesses associées

Weaknesses related to CWE-104

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Ressources

Further reading

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