CWE-102 Variant Incomplete

Struts: Duplicate Validation Forms

This vulnerability occurs when an application defines multiple Struts validation forms with identical names. The framework then unpredictably selects only one form for validation, potentially…

Definition

What is CWE-102?

This vulnerability occurs when an application defines multiple Struts validation forms with identical names. The framework then unpredictably selects only one form for validation, potentially bypassing intended security checks.
When duplicate validation form names exist, the Struts Validator picks one form arbitrarily and ignores the others. This can lead to the application validating user input against the wrong set of rules, creating unexpected security gaps. Developers might assume their defined validation is active, while in reality, a different—and possibly weaker—set of rules is being applied. This situation often signals outdated or inconsistent validation logic within the codebase. It serves as a clear indicator that the validation configuration is not being properly managed, which frequently accompanies other, more subtle flaws in input handling and data sanitization processes.
Real-world impact

Real-world CVEs caused by CWE-102

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

How attackers exploit it

Step-by-step attacker path

  1. 1

    Identify a code path that handles untrusted input without validation.

  2. 2

    Craft a payload that exercises the unsafe behavior — injection, traversal, overflow, or logic abuse.

  3. 3

    Deliver the payload through a normal request and observe the application's reaction.

  4. 4

    Iterate until the response leaks data, executes attacker code, or escalates privileges.

Vulnerable code example

Vulnerable XML

These two Struts validation forms have the same name.

Vulnerable XML 
<form-validation> 
  	 <formset> 
  		 <form name="ProjectForm"> ... </form>
  		 <form name="ProjectForm"> ... </form> 
  	 </formset> 
   </form-validation>
Secure code example

Secure pseudo

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-102

  • Implementation The DTD or schema validation will not catch the duplicate occurrence of the same form name. To find the issue in the implementation, manual checks or automated static analysis could be applied to the xml configuration files.
Detection signals

How to detect CWE-102

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.

Plexicus auto-fix

Plexicus auto-detects CWE-102 and opens a fix PR in under 60 seconds.

Codex Remedium scans every commit, identifies this exact weakness, and ships a reviewer-ready pull request with the patch. No tickets. No hand-offs.

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Frequently asked questions

Frequently asked questions

What is CWE-102?

This vulnerability occurs when an application defines multiple Struts validation forms with identical names. The framework then unpredictably selects only one form for validation, potentially bypassing intended security checks.

How serious is CWE-102?

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-102?

MITRE lists the following affected platforms: Java.

How can I prevent CWE-102?

The DTD or schema validation will not catch the duplicate occurrence of the same form name. To find the issue in the implementation, manual checks or automated static analysis could be applied to the xml configuration files.

How does Plexicus detect and fix CWE-102?

Plexicus's SAST engine matches the data-flow signature for CWE-102 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-102?

MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/102.html. You can also reference OWASP and NIST documentation for adjacent guidance.

Related weaknesses

Weaknesses related to CWE-102

CWE-694 Parent

Use of Multiple Resources with Duplicate Identifier

This vulnerability occurs when a system uses multiple resources that can share the same identifier, even though the application logic…

CWE-462 Sibling

Duplicate Key in Associative List (Alist)

This vulnerability occurs when an associative list (alist) contains duplicate keys, which can cause unexpected behavior when software…

Resources

Further reading

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