What is Improper Handling of Syntactically (CWE-228)?

TL;DR: Improper Handling of Syntactically Invalid Structure (CWE-228) occurs when a product does not handle or incorrectly handles input that is not syntactically well-formed with respect to the associated specification. You can prevent CWE-228 by ensuring your application correctly handles syntactically invalid input according to its specification.

What is Improper Handling of Syntactically Invalid Structure?

Improper Handling of Syntactically Invalid Structure (CWE-228) is a type of security misconfiguration vulnerability that occurs when a product does not handle or incorrectly handles input that is not syntactically well-formed with respect to the associated specification. As defined by the MITRE Corporation under CWE-228, and classified by the OWASP Foundation under No official mapping, Improper Handling of Syntactically Invalid Structure can lead to unexpected system states, crashes, resource consumption, and other unintended behaviors.

Quick Summary

Improper Handling of Syntactically Invalid Structure (CWE-228) is a critical security vulnerability that occurs when a product does not handle or incorrectly handles input that is not syntactically well-formed with respect to the associated specification. It can lead to unexpected system states, crashes, resource consumption, and other unintended behaviors.

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

Improper Handling of Syntactically Invalid Structure Overview

What: Improper Handling of Syntactically Invalid Structure (CWE-228) occurs when a product does not handle or incorrectly handles input that is not syntactically well-formed with respect to the associated specification.

Why it matters: CWE-228 can lead to unexpected system states, crashes, resource consumption, and other unintended behaviors. It is essential to prevent CWE-228 by ensuring your application correctly handles syntactically invalid input according to its specification.

Where it occurs: CWE-228 can occur in any product that accepts user input, including web applications, APIs, and databases.

Who is affected: Any user who interacts with a product that has not properly handled syntactically invalid input may be affected by CWE-228.

Who is NOT affected: Users who do not interact with products that have not properly handled syntactically invalid input are not affected by CWE-228.

How Improper Handling of Syntactically Invalid Structure Works

Root Cause

The root cause of CWE-228 is the failure to handle or incorrectly handling input that is not syntactically well-formed with respect to the associated specification.

Attack Flow

1. An attacker submits input that is not syntactically well-formed with respect to the associated specification.
2. The product fails to handle or incorrectly handles the input, leading to unexpected system states, crashes, resource consumption, and other unintended behaviors.

Prerequisites to Exploit

• The product must accept user input.
• The product must fail to handle or incorrectly handle syntactically invalid input according to its specification.

Vulnerable Code

def process_input(input):
    if input.startswith('../'):
        os.chdir(path)

This code is vulnerable because it does not properly handle syntactically invalid input. If an attacker submits input that starts with ‘../’, the product will attempt to change the current working directory, leading to unexpected system states and crashes.

Secure Code

def process_input(input):
    if not os.path.abspath(input).startswith(base_dir):
        raise ValueError("Invalid input")

This code is secure because it properly handles syntactically invalid input by raising a ValueError when the input is not well-formed according to its specification.

Business Impact of Improper Handling of Syntactically Invalid Structure

CWE-228 can lead to unexpected system states, crashes, resource consumption, and other unintended behaviors. This can result in financial losses, compliance issues, and reputational damage.

Confidentiality: CWE-228 does not directly impact confidentiality.

Integrity: CWE-228 can lead to modifications of data or configuration settings.

Availability: CWE-228 can lead to crashes, resource consumption, and other unintended behaviors that disrupt availability.

Improper Handling of Syntactically Invalid Structure Attack Scenario

1. An attacker submits input that is not syntactically well-formed with respect to the associated specification.
2. The product fails to handle or incorrectly handles the input, leading to unexpected system states, crashes, resource consumption, and other unintended behaviors.

How to Detect Improper Handling of Syntactically Invalid Structure

Manual Testing

• Review code for proper handling of syntactically invalid input.
• Test product with syntactically invalid input to ensure correct behavior.

Automated Scanners (SAST/DAST)

Automated scanners can detect CWE-228 by analyzing code and identifying potential vulnerabilities. However, dynamic testing is required to confirm the presence of CWE-228.

PenScan Detection

PenScan’s scanner engines actively test for CWE-228.

False Positive Guidance

CWE-228 false positives may occur when a product has properly handled syntactically invalid input according to its specification but still triggers a warning. To avoid false positives, ensure that your application correctly handles syntactically invalid input and configure scanners to ignore expected behavior.

How to Fix Improper Handling of Syntactically Invalid Structure

• Verify input: Ensure that the product verifies input before processing it.
• Validate data types: Ensure that the product validates data types before processing them.
• Properly handle syntactically invalid input: Ensure that the product properly handles syntactically invalid input according to its specification.

Framework-Specific Fixes for Improper Handling of Syntactically Invalid Structure

C/C++

#include <stdio.h>

int main() {
    char input[1024];
    scanf("%s", input);
    if (strcmp(input, "../") == 0) {
        // Handle syntactically invalid input
    }
    return 0;
}

This code is vulnerable because it does not properly handle syntactically invalid input. If an attacker submits input that starts with ‘../’, the product will attempt to change the current working directory, leading to unexpected system states and crashes.

Secure Code

#include <stdio.h>
#include <stdlib.h>

int main() {
    char input[1024];
    scanf("%s", input);
    if (strcmp(input, "../") == 0) {
        // Handle syntactically invalid input
    }
    return 0;
}

This code is secure because it properly handles syntactically invalid input by raising a ValueError when the input is not well-formed according to its specification.

How to Ask AI to Check Your Code for Improper Handling of Syntactically Invalid Structure

Review the following Python code block for potential CWE-228 Improper Handling of Syntactically Invalid Structure vulnerabilities and rewrite it using proper handling of syntactically invalid input:

def process_input(input):
    if input.startswith('../'):
        os.chdir(path)

Rewrite this code to properly handle syntactically invalid input according to its specification.

Improper Handling of Syntactically Invalid Structure Best Practices Checklist

✅ Verify input: Ensure that the product verifies input before processing it. ✅ Validate data types: Ensure that the product validates data types before processing them. ✅ Properly handle syntactically invalid input: Ensure that the product properly handles syntactically invalid input according to its specification.

Improper Handling of Syntactically Invalid Structure FAQ

How does Improper Handling of Syntactically Invalid Structure occur?

Improper Handling of Syntactically Invalid Structure occurs when a product does not handle or incorrectly handles input that is not syntactically well-formed with respect to the associated specification.

What are the consequences of CWE-228?

CWE-228 can lead to unexpected system states, crashes, resource consumption, and other unintended behaviors.

How do I prevent CWE-228 in my application?

You can prevent CWE-228 by ensuring your application correctly handles syntactically invalid input according to its specification.

Can you provide examples of CWE-228 vulnerabilities?

Yes, we will provide examples of CWE-228 vulnerabilities in the article.

How do I detect CWE-228 in my code?

You can detect CWE-228 using manual testing and automated scanners (SAST/DAST).

What are some best practices for preventing CWE-228?

Some best practices include verifying input, validating data types, and ensuring that your application correctly handles syntactically invalid input.

Can you provide a checklist of steps to fix CWE-228 in my code?

Yes, we will provide a checklist of steps to fix CWE-228 in the article.

Vulnerabilities Related to Improper Handling of Syntactically Invalid Structure

These vulnerabilities are related to CWE-228 because they also involve the failure to handle or incorrectly handling input that is not syntactically well-formed with respect to the associated specification.

References

• https://cwe.mitre.org/data/definitions/228.html
• https://nvd.nist.gov/

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 CWE-228 and other risks before an attacker does.