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CWE-105 Variant Draft
Struts: Form Field Without Validator
This vulnerability occurs when a Struts application form contains an input field that lacks a corresponding validator, leaving it open to unverified user input.
Definition
What is CWE-105?
This vulnerability occurs when a Struts application form contains an input field that lacks a corresponding validator, leaving it open to unverified user input.
Leaving even one form field without validation creates a direct opening for attackers. They can exploit this oversight to inject malicious data, bypass security checks, or manipulate application logic, potentially leading to data breaches, unauthorized access, or system compromise.
While Java applications themselves are often protected from low-level memory issues, the risk escalates if the application interacts with native code or external systems. An attacker could use this unvalidated input as an entry point to trigger buffer overflows or other critical vulnerabilities in those connected components, turning a simple input oversight into a severe chained attack.
Auswirkungen in der Praxis
Real-world CVEs caused by CWE-105
Bisher sind in MITREs Katalog keine öffentlichen CVE-Referenzen mit dieser CWE verknüpft.
Wie Angreifer es ausnutzen
Angreiferpfad Schritt für Schritt
- 1
In the following example the Java class RegistrationForm is a Struts framework ActionForm Bean that will maintain user input data 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 in the form fields using the private member variables. The RegistrationForm class uses the Struts validation capability by extending the ValidatorForm class and including the validation for the form fields within the validator XML file, validator.xml.
- 2
The validator XML file, validator.xml, provides the validation for the form fields of the RegistrationForm.
- 3
However, in the previous example the validator XML file, validator.xml, does not provide validators for all of the form fields in the RegistrationForm. Validator forms are only provided for the first five of the seven form fields. The validator XML file should contain validator forms for all of the form fields for a Struts ActionForm bean. The following validator.xml file for the RegistrationForm class contains validator forms for all of the form fields.
Verwundbares Codebeispiel
Vulnerable XML
The validator XML file, validator.xml, provides the validation for the form fields of the RegistrationForm.
<form-validation>
<formset>
<form name="RegistrationForm">
<field property="name" depends="required">
<arg position="0" key="prompt.name"/>
</field>
<field property="address" depends="required">
<arg position="0" key="prompt.address"/>
</field>
<field property="city" depends="required">
<arg position="0" key="prompt.city"/>
</field>
<field property="state" depends="required,mask">
<arg position="0" key="prompt.state"/>
<var>
<var-name>mask</var-name>
<var-value>[a-zA-Z]{2}</var-value>
</var>
</field>
<field property="zipcode" depends="required,mask">
<arg position="0" key="prompt.zipcode"/>
<var>
<var-name>mask</var-name>
<var-value>\d{5}</var-value>
</var>
</field>
</form>
</formset>
</form-validation> Sicheres Codebeispiel
Secure XML
However, in the previous example the validator XML file, validator.xml, does not provide validators for all of the form fields in the RegistrationForm. Validator forms are only provided for the first five of the seven form fields. The validator XML file should contain validator forms for all of the form fields for a Struts ActionForm bean. The following validator.xml file for the RegistrationForm class contains validator forms for all of the form fields.
<form-validation>
<formset>
<form name="RegistrationForm">
<field property="name" depends="required">
<arg position="0" key="prompt.name"/>
</field>
<field property="address" depends="required">
<arg position="0" key="prompt.address"/>
</field>
<field property="city" depends="required">
<arg position="0" key="prompt.city"/>
</field>
<field property="state" depends="required,mask">
<arg position="0" key="prompt.state"/>
<var>
<var-name>mask</var-name>
<var-value>[a-zA-Z]{2}</var-value>
</var>
</field>
<field property="zipcode" depends="required,mask">
<arg position="0" key="prompt.zipcode"/>
<var>
<var-name>mask</var-name>
<var-value>\d{5}</var-value>
</var>
</field>
<field property="phone" depends="required,mask">
<arg position="0" key="prompt.phone"/>
<var>
<var-name>mask</var-name>
<var-value>^([0-9]{3})(-)([0-9]{4}|[0-9]{4})$</var-value>
</var>
</field>
<field property="email" depends="required,email">
<arg position="0" key="prompt.email"/>
</field>
</form>
</formset>
</form-validation> What changed: the unsafe sink is replaced (or the input is validated/escaped) so the same payload no longer triggers the weakness.
Präventions-Checkliste
How to prevent CWE-105
- Implementation Validate all form fields. If a field is unused, it is still important to constrain it so that it is empty or undefined.
Erkennungssignale
How to detect CWE-105
Führe dynamische Application-Security-Tests gegen den Live-Endpoint aus.
Beobachte Runtime-Logs auf ungewöhnliche Exception-Traces, fehlerhafte Eingaben oder Versuche, Autorisierung zu umgehen.
Code Review: Markiere jeden neuen Code, der Eingaben von dieser Oberfläche ohne validierte Framework-Helper verarbeitet.
CWE-105
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.
Häufig gestellte Fragen Was ist CWE-105?
Wie gravierend ist CWE-105?
Welche Sprachen oder Plattformen sind von CWE-105 betroffen?
Wie kann ich CWE-105 verhindern?
Wie erkennt und behebt Plexicus CWE-105?
Wo erfahre ich mehr über CWE-105?
Frequently asked questions
Was ist CWE-105?
This vulnerability occurs when a Struts application form contains an input field that lacks a corresponding validator, leaving it open to unverified user input.
Wie gravierend ist CWE-105?
MITRE hat für diese Schwachstelle keine Exploit-Wahrscheinlichkeit veröffentlicht. Behandle sie als mittlere Auswirkung, bis dein Threat Model anderes belegt.
Welche Sprachen oder Plattformen sind von CWE-105 betroffen?
MITRE lists the following affected platforms: Java.
Wie kann ich CWE-105 verhindern?
Validate all form fields. If a field is unused, it is still important to constrain it so that it is empty or undefined.
Wie erkennt und behebt Plexicus CWE-105?
Die SAST-Engine von Plexicus erkennt die Datenfluss-Signatur von CWE-105 bei jedem Commit. Bei einem Treffer öffnet unser Codex-Remedium-Agent einen Fix-PR mit korrigiertem Code, Tests und einer einzeiligen Zusammenfassung für den Reviewer.
Wo erfahre ich mehr über CWE-105?
MITRE veröffentlicht die kanonische Definition unter https://cwe.mitre.org/data/definitions/105.html. Für ergänzende Hinweise kannst du auch die OWASP- und NIST-Dokumentation heranziehen.
Verwandte Schwachstellen
Weaknesses related to CWE-105
CWE-1173 Parent
Improper Use of Validation Framework
This vulnerability occurs when a software application either fails to use or incorrectly implements a built-in or library-provided input…
CWE-102 Sibling
Struts: Duplicate Validation Forms
This vulnerability occurs when an application defines multiple Struts validation forms with identical names. The framework then…
CWE-106 Sibling
Struts: Plug-in Framework not in Use
This weakness occurs when a Java application, particularly one using the Struts framework, does not implement a structured input…
CWE-108 Sibling
Struts: Unvalidated Action Form
In Apache Struts, every Action Form that processes user input must have a corresponding validation form configured. Missing this…
CWE-109 Sibling
Struts: Validator Turned Off
This vulnerability occurs when an application built with Apache Struts intentionally disables its built-in validation framework. By…
CWE-1174 Sibling
ASP.NET Misconfiguration: Improper Model Validation
This vulnerability occurs when an ASP.NET application either completely bypasses the built-in model validation system or implements it…
CWE-554 Sibling
ASP.NET Misconfiguration: Not Using Input Validation Framework
This vulnerability occurs when an ASP.NET application fails to implement a structured input validation framework, relying instead on…
Ressourcen
Further reading
- MITRE — offizielle CWE-105 https://cwe.mitre.org/data/definitions/105.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
Bereit, das Wesentliche zu validieren?
Bereit zu validieren, was zählt.
Plexicus ist Proof-Driven AppSec: validierte Funde, kontextuelles Verständnis und geprüfte Remediation — in Evidenz verankert, mit Ihnen gescoped.