What is Permissive List of Allowed Inputs (CWE-183)?

TL;DR: Permissive List of Allowed Inputs (CWE-183) is a type of Insecure Design vulnerability that occurs when a protection mechanism relies on a list of inputs or properties of inputs that are explicitly allowed by policy, but the list is too permissive and allows an input that is unsafe.

What is Permissive List of Allowed Inputs?

Permissive List of Allowed Inputs (CWE-183) is a type of Insecure Design vulnerability that occurs when a protection mechanism relies on a list of inputs or properties of inputs that are explicitly allowed by policy, but the list is too permissive and allows an input that is unsafe. As defined by the MITRE Corporation under CWE-183, and classified by the OWASP Foundation under A06:2025 - Insecure Design, this vulnerability can allow unauthorized access to sensitive data, potentially leading to security breaches and financial losses due to reputational damage and compliance issues.

Quick Summary

Permissive List of Allowed Inputs (CWE-183) is a type of Insecure Design vulnerability that occurs when a protection mechanism relies on a list of inputs or properties of inputs that are explicitly allowed by policy, but the list is too permissive and allows an input that is unsafe. This can allow unauthorized access to sensitive data, potentially leading to security breaches and financial losses due to reputational damage and compliance issues.

Jump to: Quick Summary · Permissive List of Allowed Inputs Overview · How Permissive List of Allowed Inputs Works · Business Impact of Permissive List of Allowed Inputs · Permissive List of Allowed Inputs Attack Scenario · How to Detect Permissive List of Allowed Inputs · How to Fix Permissive List of Allowed Inputs · Framework-Specific Fixes for Permissive List of Allowed Inputs · How to Ask AI to Check Your Code for Permissive List of Allowed Inputs · Permissive List of Allowed Inputs Best Practices Checklist · Permissive List of Allowed Inputs FAQ · Vulnerabilities Related to Permissive List of Allowed Inputs · References · Scan Your Own Site

Permissive List of Allowed Inputs Overview

What: Permissive List of Allowed Inputs (CWE-183) is a type of Insecure Design vulnerability that occurs when a protection mechanism relies on a list of inputs or properties of inputs that are explicitly allowed by policy, but the list is too permissive and allows an input that is unsafe.

Why it matters: CWE-183 can allow unauthorized access to sensitive data, potentially leading to security breaches and financial losses due to reputational damage and compliance issues.

Where it occurs: CWE-183 can occur in any system or application that uses input validation mechanisms.

Who is affected: Any user who inputs data into a system or application that uses input validation mechanisms is at risk of being affected by CWE-183.

Who is NOT affected: Users who do not input data into systems or applications that use input validation mechanisms are not at risk of being affected by CWE-183.

How Permissive List of Allowed Inputs Works

Root Cause

Permissive List of Allowed Inputs (CWE-183) occurs when a protection mechanism relies on a list of inputs or properties of inputs that are explicitly allowed by policy, but the list is too permissive and allows an input that is unsafe.

Attack Flow

1. An attacker inputs data into a system or application that uses input validation mechanisms.
2. The input validation mechanism checks if the input is in the list of allowed inputs.
3. If the input is in the list, it is processed as valid input.
4. However, if the list is too permissive and allows an input that is unsafe, the attacker can bypass the protection mechanism and access sensitive data.

Prerequisites to Exploit

• The system or application must use input validation mechanisms.
• The list of allowed inputs must be too permissive and allow an input that is unsafe.
• The attacker must have knowledge of the input validation mechanism and the list of allowed inputs.

Vulnerable Code

def validate_input(input):
    if input in allowed_inputs:
        return True
    else:
        raise ValueError("Invalid input")

This code demonstrates a vulnerable input validation mechanism that allows an input that is unsafe because the list of allowed inputs is too permissive.

Secure Code

def validate_input(input):
    if input not in allowed_inputs:
        raise ValueError("Invalid input")

This code demonstrates a secure input validation mechanism that does not allow an input that is unsafe by checking if the input is in the list of allowed inputs before processing it as valid input.

Business Impact of Permissive List of Allowed Inputs

The business impacts of CWE-183 include:

• Financial losses due to security breaches
• Reputational damage
• Compliance issues

These impacts can occur when an attacker bypasses the protection mechanism and accesses sensitive data, potentially leading to unauthorized access, data theft, or other malicious activities.

Permissive List of Allowed Inputs Attack Scenario

1. An attacker inputs data into a system or application that uses input validation mechanisms.
2. The input validation mechanism checks if the input is in the list of allowed inputs.
3. If the input is in the list, it is processed as valid input.
4. However, if the list is too permissive and allows an input that is unsafe, the attacker can bypass the protection mechanism and access sensitive data.

How to Detect Permissive List of Allowed Inputs

Manual Testing

• Review the code for input validation mechanisms.
• Check the list of allowed inputs for any overly permissive entries.
• Test the system or application with malicious inputs to ensure that the protection mechanism is effective.

Automated Scanners (SAST / DAST)

• Use automated scanners to identify potential vulnerabilities in the system or application.
• The scanners can detect CWE-183 by identifying overly permissive lists of allowed inputs.

PenScan Detection

PenScan’s scanner engines actively test for this issue and can help detect CWE-183.

False Positive Guidance

When reviewing the results of automated scanning, be aware that some findings may be false positives due to context. For example, a pattern that looks risky but is actually safe because it is in a specific directory or has a specific prefix.

How to Fix Permissive List of Allowed Inputs

• Review the list of allowed inputs and remove any overly permissive entries.
• Implement robust input validation mechanisms to ensure that only valid inputs are processed.
• Test the system or application with malicious inputs to ensure that the protection mechanism is effective.

Framework-Specific Fixes for Permissive List of Allowed Inputs

Java

public class InputValidator {
    private Set<String> allowedInputs;

    public boolean validateInput(String input) {
        if (allowedInputs.contains(input)) {
            return true;
        } else {
            throw new IllegalArgumentException("Invalid input");
        }
    }
}

This code demonstrates a secure input validation mechanism in Java that checks if the input is in the list of allowed inputs before processing it as valid input.

Node.js

const InputValidator = {
  validateInput: function(input) {
    if (allowedInputs.includes(input)) {
      return true;
    } else {
      throw new Error("Invalid input");
    }
  }
};

This code demonstrates a secure input validation mechanism in Node.js that checks if the input is in the list of allowed inputs before processing it as valid input.

Python/Django

class InputValidator:
    def __init__(self):
        self.allowed_inputs = set()

    def validate_input(self, input):
        if input in self.allowed_inputs:
            return True
        else:
            raise ValueError("Invalid input")

This code demonstrates a secure input validation mechanism in Python/Django that checks if the input is in the list of allowed inputs before processing it as valid input.

PHP

class InputValidator {
    private $allowedInputs;

    public function validateInput($input) {
        if (in_array($input, $this->allowedInputs)) {
            return true;
        } else {
            throw new InvalidArgumentException("Invalid input");
        }
    }
}

This code demonstrates a secure input validation mechanism in PHP that checks if the input is in the list of allowed inputs before processing it as valid input.

How to Ask AI to Check Your Code for Permissive List of Allowed Inputs

To ask an AI-powered tool like PenScan’s scanner engines to check your code for CWE-183, you can use a prompt like:

Review the following Python/Django code block for potential CWE-183 Permissive List of Allowed Inputs vulnerabilities and rewrite it using robust input validation mechanisms:

class InputValidator:
    def __init__(self):
        self.allowed_inputs = set()

    def validate_input(self, input):
        if input in self.allowed_inputs:
            return True
        else:
            raise ValueError("Invalid input")

Permissive List of Allowed Inputs Best Practices Checklist

✅ Review the list of allowed inputs and remove any overly permissive entries. ✅ Implement robust input validation mechanisms to ensure that only valid inputs are processed. ✅ Test the system or application with malicious inputs to ensure that the protection mechanism is effective.

Permissive List of Allowed Inputs FAQ

How does CWE-183 occur?

CWE-183 occurs when a protection mechanism relies on a list of inputs or properties of inputs that are explicitly allowed by policy, but the list is too permissive and allows an input that is unsafe.

What are the consequences of CWE-183?

The consequences of CWE-183 include bypassing protection mechanisms, allowing unauthorized access to sensitive data, and potentially leading to security breaches.

How can I prevent CWE-183?

To prevent CWE-183, ensure that your input validation mechanisms are robust and do not allow overly permissive lists of allowed inputs.

Can AI help detect CWE-183?

Yes, AI-powered tools like PenScan’s scanner engines can help detect CWE-183 by identifying potential vulnerabilities in your code.

What are the business impacts of CWE-183?

The business impacts of CWE-183 include financial losses due to security breaches, reputational damage, and compliance issues.

How common is CWE-183?

CWE-183 is a relatively common vulnerability that can occur in any system or application that uses input validation mechanisms.

Can I fix CWE-183 manually?

Yes, you can fix CWE-183 manually by reviewing your code and ensuring that your input validation mechanisms are robust and do not allow overly permissive lists of allowed inputs.

Vulnerabilities Related to Permissive List of Allowed Inputs

These vulnerabilities are related to CWE-183 because they can also lead to security breaches and financial losses due to reputational damage and compliance issues.

References

• MITRE: CWE-183
• OWASP: A06:2025 - Insecure Design
• CAPEC: CAPEC-120, CAPEC-3, CAPEC-43, CAPEC-71
• NVD

Scan Your Own Site

Manual code review catches what you know to look for. An automated scan catches what you didn’t. Scan your own website using PenScan to find Permissive List of Allowed Inputs and other risks before an attacker does.