CWE-108 Variant Incomplete

Struts: Unvalidated Action Form

In Apache Struts, every Action Form that processes user input must have a corresponding validation form configured. Missing this validation exposes the application to unvalidated data.

Definition

What is CWE-108?

In Apache Struts, every Action Form that processes user input must have a corresponding validation form configured. Missing this validation exposes the application to unvalidated data.
This vulnerability occurs when a Struts configuration maps an Action Form but fails to link it to a validation form via the Struts Validator framework. Without this link, user-submitted data flows directly into your application logic and backend systems without any automatic checks, making it a prime target for injection attacks and data corruption. To fix this, you must ensure that for every `` mapping that specifies a `name` attribute (pointing to a form bean), a corresponding validation rule is defined in the `validation.xml` file. This setup enforces that all input meets your defined criteria before the associated Action class executes, closing a critical security gap in your request handling pipeline.
Real-world impact

Real-world CVEs caused by CWE-108

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 pseudo

MITRE has not published a code example for this CWE. The pattern below is illustrative — see Resources for canonical references.

Vulnerable pseudo 
// Example pattern — see MITRE for the canonical references.
function handleRequest(input) {
  // Untrusted input flows directly into the sensitive sink.
  return executeUnsafe(input);
}
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-108

  • Implementation Map every Action Form to a corresponding validation form. An action or a form may perform validation in other ways, but the Struts Validator provides an excellent way to verify that all input receives at least a basic level of validation. Without this approach, it is difficult, and often impossible, to establish with a high level of confidence that all input is validated.
Detection signals

How to detect CWE-108

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-108 and opens a fix PR in under 60 seconds.

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Frequently asked questions

Frequently asked questions

What is CWE-108?

In Apache Struts, every Action Form that processes user input must have a corresponding validation form configured. Missing this validation exposes the application to unvalidated data.

How serious is CWE-108?

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-108?

MITRE lists the following affected platforms: Java.

How can I prevent CWE-108?

Map every Action Form to a corresponding validation form. An action or a form may perform validation in other ways, but the Struts Validator provides an excellent way to verify that all input receives at least a basic level of validation. Without this approach, it is difficult, and often impossible, to establish with a high level of confidence that all input is validated.

How does Plexicus detect and fix CWE-108?

Plexicus's SAST engine matches the data-flow signature for CWE-108 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-108?

MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/108.html. You can also reference OWASP and NIST documentation for adjacent guidance.

Related weaknesses

Weaknesses related to CWE-108

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-105 Sibling

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…

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-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…

Resources

Further reading

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