What is Improper Validation of Function Hook (CWE-622)?

TL;DR: Improper Validation of Function Hook Arguments (CWE-622) is a security vulnerability where user-accessible API functions receive unvalidated inputs, leading to unexpected state changes and integrity issues. To fix it, validate all arguments against expected values or ranges.

What is Improper Validation of Function Hook Arguments?

Improper Validation of Function Hook Arguments (CWE-622) is a type of security vulnerability that occurs when a product adds hooks to user-accessible API functions without properly validating the arguments. As defined by the MITRE Corporation under CWE-622, and classified by the OWASP Foundation under [mapping], this weakness can lead to resultant vulnerabilities.

Quick Summary

Improper Validation of Function Hook Arguments is critical because it allows attackers to manipulate function hooks with unvalidated inputs, leading to unexpected state changes or integrity issues. Jump to: Overview · How It Works · Business Impact · Attack Scenario · Detection · Fixes

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

Improper Validation of Function Hook Arguments Overview

What

Improper Validation of Function Hook Arguments is a security vulnerability where arguments passed to user-accessible API functions are not properly validated.

Why it matters

Proper validation ensures that only safe and expected inputs are processed, preventing unexpected state changes or integrity issues. Without proper validation, attackers can manipulate function hooks with malicious input.

Where it occurs

This weakness commonly appears in applications that expose APIs for configuration management, user settings, or other sensitive operations without adequate argument validation.

Who is affected

Developers who implement API functions without validating inputs are at risk of introducing this vulnerability into their systems.

Who is NOT affected

Applications that enforce strict input validation and verification mechanisms before processing function hook arguments are not vulnerable to this issue.

How Improper Validation of Function Hook Arguments Works

Root Cause

The root cause lies in the lack of proper argument validation for API functions, allowing untrusted inputs to manipulate system configurations or states without appropriate checks.

Attack Flow

1. An attacker identifies an exposed API function that accepts user input.
2. The attacker sends maliciously crafted arguments to the hook.
3. The application processes the unvalidated input, leading to unexpected state changes or integrity issues.

Prerequisites to Exploit

• Exposed API functions with insufficient argument validation.
• User inputs that can be manipulated by an attacker.

Vulnerable Code

def update_setting(setting_name, value):
    # No validation of setting_name and value
    config[setting_name] = value

This code is vulnerable because it does not validate the setting_name or value, allowing attackers to modify configuration settings with untrusted inputs.

Secure Code

def update_setting(setting_name, value):
    if setting_name in allowed_settings and isinstance(value, str):
        config[setting_name] = value

This code is secure because it checks that the setting_name exists in a predefined list of allowed settings and ensures that value is a string before updating the configuration.

Business Impact of Improper Validation of Function Hook Arguments

Integrity

• Example: An attacker modifies system configurations by sending unvalidated inputs to API functions.
• Consequence: Unauthorized changes can disrupt normal operations, leading to data corruption or service outages.

Financial

• Losses due to downtime and recovery efforts after unauthorized configuration modifications.
• Increased costs for incident response and remediation activities.

Compliance

• Non-compliance with regulatory requirements if sensitive settings are altered without proper validation.
• Potential fines from regulatory bodies for failing to protect system configurations adequately.

Improper Validation of Function Hook Arguments Attack Scenario

1. An attacker identifies an API endpoint that allows users to modify configuration settings.
2. The attacker sends a request with maliciously crafted arguments to the endpoint.
3. The application processes the unvalidated input, leading to unauthorized changes in system configurations.
4. The attacker exploits the modified settings to gain further access or control over the system.

How to Detect Improper Validation of Function Hook Arguments

Manual Testing

• Review API functions for proper argument validation before processing inputs.
• Verify that all user-accessible endpoints enforce strict input checks and validations.
• Test the application with maliciously crafted arguments to identify unvalidated inputs.

Automated Scanners (SAST / DAST)

Static analysis can detect missing validation logic, while dynamic testing can simulate attacks to verify proper handling of untrusted inputs.

PenScan Detection

PenScan’s automated scanners actively test for improper validation by simulating malicious inputs and verifying proper argument validation.

• ZAP
• Nuclei
• Wapiti

False Positive Guidance

A finding is likely a false positive if the input is validated through other mechanisms (e.g., client-side validation) that are not detected by static analysis.

How to Fix Improper Validation of Function Hook Arguments

• Ensure all arguments passed to API functions are verified against expected values or ranges before processing.
• Implement strict input checks and validations for user-accessible endpoints.
• Drop privileges before invoking such functions, if possible.

Framework-Specific Fixes for Improper Validation of Function Hook Arguments

Python/Django

def update_setting(setting_name, value):
    if setting_name in settings.ALLOWED_SETTINGS and isinstance(value, str):
        config[setting_name] = value

Java

public void updateSetting(String settingName, String value) {
    if (allowedSettings.contains(settingName)) {
        config.put(settingName, value);
    }
}

How to Ask AI to Check Your Code for Improper Validation of Function Hook Arguments

Improper Validation of Function Hook Arguments Best Practices Checklist

• ✅ Verify all arguments passed to API functions are validated against expected values or ranges.
• ✅ Implement strict input checks for user-accessible endpoints.
• ✅ Drop privileges before invoking critical functions, if possible.

Improper Validation of Function Hook Arguments FAQ

How does improper validation of function hook arguments occur?

It occurs when a product adds hooks to user-accessible API functions without properly validating the arguments, leading to vulnerabilities.

Why is it important to validate function hook arguments?

Validation ensures that only safe and expected inputs are processed, preventing unexpected state changes or integrity issues.

Can you provide an example of improper validation in a real-world application?

Consider an API endpoint that allows users to modify settings without validating the input values, leading to unauthorized configuration changes.

How do I detect improper validation of function hook arguments manually?

Review code for hooks added to user-accessible APIs and ensure all arguments are validated before being processed.

What is a common fix for improper validation of function hook arguments?

Ensure that all arguments passed to API functions are verified against expected values or ranges.

How does PenScan help prevent Improper Validation of Function Hook Arguments?

PenScan’s automated scanners actively test for improper validation by simulating malicious inputs and verifying proper argument validation.

Vulnerabilities Related to Improper Validation of Function Hook Arguments

References

• MITRE: Improper Validation of Function Hook Arguments
• NVD - National Vulnerability Database

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 Improper Validation of Function Hook Arguments and other risks before an attacker does.