CWE-107 Variant Draft

Struts: Unused Validation Form

This vulnerability occurs when a Struts application contains validation form definitions that are no longer linked to any active form or action, leaving outdated security rules in the codebase.

Definition

What is CWE-107?

This vulnerability occurs when a Struts application contains validation form definitions that are no longer linked to any active form or action, leaving outdated security rules in the codebase.

In Struts frameworks, validation logic is often tied to specific form or action mappings. When developers rename or remove these mappings during refactoring, they can easily overlook the corresponding validation forms. These orphaned validation rules remain in the configuration files, creating a false sense of security and cluttering the code with dead logic. This situation is problematic because it indicates that the application's validation layer is not being properly maintained. Attackers may exploit the gap between the actual form processing and the intended validation rules, potentially bypassing client-side or server-side checks. Regularly auditing and removing unused validation forms is essential to keep security configurations accurate and effective.

Real-world impact

Real-world CVEs caused by CWE-107

No public CVE references are linked to this CWE in MITRE's catalog yet.

How attackers exploit it

Step-by-step attacker path

1
In the following example the 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
However, the validator XML file, validator.xml, for the RegistrationForm class includes the validation form for the user input form field "phone" that is no longer used by the input form and the RegistrationForm class. Any validation forms that are no longer required should be removed from the validator XML file, validator.xml.
3
The existence of unused forms may be an indication to attackers that this code is out of date or poorly maintained.

Vulnerable code example

Vulnerable Java

In the following example the 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.

Vulnerable Java

public class RegistrationForm extends org.apache.struts.validator.ValidatorForm {
```
// private variables for registration form* 
  		private String name;
  		private String address;
  		private String city;
  		private String state;
  		private String zipcode;
  		
  		 *// no longer using the phone form field* 
  		
  		
  		 *// private String phone;* 
  		private String email;
  		
  		public RegistrationForm() {
  		```
  			super();
  		}
```
// getter and setter methods for private variables* 
  		...}

Secure code example

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.

Prevention checklist

How to prevent CWE-107

Implementation Remove the unused Validation Form from the validation.xml file.

Detection signals

How to detect CWE-107

SAST High

Run static analysis (SAST) on the codebase looking for the unsafe pattern in the data flow.

DAST Moderate

Run dynamic application security testing against the live endpoint.

Runtime Moderate

Watch runtime logs for unusual exception traces, malformed input, or authorization bypass attempts.

Code review Moderate

Code review: flag any new code that handles input from this surface without using the validated framework helpers.

CWE-107

Don't catalog this weakness. Prove it's reachable.

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Frequently asked questions

What is CWE-107?

This vulnerability occurs when a Struts application contains validation form definitions that are no longer linked to any active form or action, leaving outdated security rules in the codebase.

How serious is CWE-107?

MITRE has not published a likelihood-of-exploit rating for this weakness. Treat it as medium-impact until your threat model proves otherwise.

What languages or platforms are affected by CWE-107?

MITRE lists the following affected platforms: Java.

How can I prevent CWE-107?

Remove the unused Validation Form from the validation.xml file.

How does Plexicus detect and fix CWE-107?

Plexicus's SAST engine matches the data-flow signature for CWE-107 on every commit. When a match is found, our Codex Remedium agent opens a fix PR with the corrected code, tests, and a one-line summary for the reviewer.

Where can I learn more about CWE-107?

MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/107.html. You can also reference OWASP and NIST documentation for adjacent guidance.

Related weaknesses

Weaknesses related to CWE-107

CWE-1164 Parent

Struts: Unused Validation Form

What is CWE-107?

Real-world CVEs caused by CWE-107

Step-by-step attacker path

Vulnerable Java

Secure pseudo

How to prevent CWE-107

How to detect CWE-107

Don't catalog this weakness. Prove it's reachable.

Frequently asked questions

Weaknesses related to CWE-107

Irrelevant Code

Empty Code Block

Struts: Validator Without Form Field

Dead Code

Assignment to Variable without Use

Further reading

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Sample evidence handover

Server-Side Request Forgery in `webhooks/receiver`