What is Improper Neutralization of Quoting Syntax (CWE-149)?

TL;DR: Improper Neutralization of Quoting Syntax (CWE-149) occurs when quotes in user input are not properly managed, leading to unexpected system behavior. Ensure robust input validation and proper handling of quotes to prevent this vulnerability.

What is Improper Neutralization of Quoting Syntax?

Improper Neutralization of Quoting Syntax (CWE-149) is a type of vulnerability where quotes injected into an application’s input are not properly handled, leading to unexpected behavior during parsing. As defined by the MITRE Corporation under CWE-149, and classified by the OWASP Foundation as Not directly mapped.

Quick Summary

Improper Neutralization of Quoting Syntax occurs when user-supplied data containing quotes is improperly managed, causing unintended actions within an application. This can lead to integrity issues, unauthorized access, or system compromise. Jump to: Overview · How It Works · Business Impact · Attack Scenario · Detection · Fixes · Framework-Specific Fixes · Ask AI · Best Practices Checklist · FAQ

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

Improper Neutralization of Quoting Syntax Overview

What:

Improper Neutralization of Quoting Syntax is a vulnerability where quotes in user input are not properly managed, leading to unexpected behavior during parsing.

Why it matters:

This can cause integrity issues and allow attackers to manipulate system actions through improperly parsed inputs.

Where it occurs:

In web applications, databases, and scripting languages that process untrusted data containing quotes.

Who is affected:

Developers of systems accepting user input without proper validation or escaping mechanisms.

Who is NOT affected:

Applications that never construct paths/queries/commands from external input.

How Improper Neutralization of Quoting Syntax Works

Root Cause

Quotes injected into a product can be used to compromise a system. As data are parsed, an injected/absent/duplicate/malformed use of quotes may cause the process to take unexpected actions.

Attack Flow

1. Attacker injects malicious input containing improperly handled quotes.
2. Application processes the input without proper sanitization or escaping.
3. Unexpected behavior occurs during parsing, leading to potential vulnerabilities.

   Prerequisites to Exploit

   • Untrusted input reaching a parsing function.
   • Lack of proper validation and escaping mechanisms.

     Vulnerable Code

     def process_input(user_input):
      parsed_data = eval(user_input)
     

     This code is vulnerable because it directly evaluates user-supplied input, allowing for improper handling of quotes.

Secure Code

def validate_and_process(user_input):
    if not re.match(r'^[a-zA-Z0-9\s]+$', user_input):
        raise ValueError("Invalid input")
    parsed_data = eval(user_input)

This code securely validates and processes the input, preventing improper handling of quotes.

Business Impact of Improper Neutralization of Quoting Syntax

Integrity

Improper neutralization can lead to data corruption or unauthorized modifications.

• Financial: Losses due to compromised data integrity.
• Compliance: Non-compliance with regulatory standards for data protection.
• Reputation: Damage to brand reputation from security breaches.

Improper Neutralization of Quoting Syntax Attack Scenario

1. Attacker injects malicious input containing improperly handled quotes into a web application’s input field.
2. The application processes the input without proper validation or escaping, leading to unexpected behavior during parsing.
3. This results in data corruption and unauthorized access to sensitive information.

How to Detect Improper Neutralization of Quoting Syntax

Manual Testing

• Check for direct use of eval() or similar functions on untrusted inputs.
• Verify that quotes are properly escaped and validated before processing.

  Automated Scanners (SAST / DAST)

  Static analysis can detect the presence of eval() calls, while dynamic testing can simulate malicious input to see if it causes unexpected behavior.

  PenScan Detection

  PenScan’s scanner engines such as ZAP, Nuclei, Wapiti, and Nikto are effective in identifying instances of improper neutralization.

  False Positive Guidance

  False positives may occur when legitimate use of quotes is flagged. Ensure that the input context is properly validated to distinguish between safe and malicious uses.

How to Fix Improper Neutralization of Quoting Syntax

• Use an appropriate combination of denylists and allowlists to ensure only valid, expected inputs are processed.
• Implement strict input validation strategies to reject or transform invalid inputs.
• Properly escape or filter special characters within arguments before processing them.

Framework-Specific Fixes for Improper Neutralization of Quoting Syntax

Python/Django

def validate_and_process(user_input):
    if not re.match(r'^[a-zA-Z0-9\s]+$', user_input):
        raise ValueError("Invalid input")
    parsed_data = eval(user_input)

This code securely validates and processes the input, preventing improper handling of quotes.

How to Ask AI to Check Your Code for Improper Neutralization of Quoting Syntax

Improper Neutralization of Quoting Syntax Best Practices Checklist

✅ Use an appropriate combination of denylists and allowlists to ensure only valid, expected inputs are processed. ✅ Implement strict input validation strategies to reject or transform invalid inputs. ✅ Properly escape or filter special characters within arguments before processing them.

Improper Neutralization of Quoting Syntax FAQ

How does improper neutralization of quoting syntax occur?

It happens when quotes are not properly handled in input data, leading to unexpected behavior during parsing.

What are the consequences of improper neutralization of quoting syntax?

This can lead to integrity issues and system compromise due to unexpected actions taken by the application.

How do you validate inputs to prevent this vulnerability?

Use input validation techniques such as denylists and allowlists to ensure only valid, expected inputs are processed.

Can you provide an example of vulnerable code for improper neutralization of quoting syntax?

Vulnerable code processes user-supplied quotes without proper sanitization or escaping.

What is the best way to fix this vulnerability in Python?

Use Python’s built-in escape mechanisms and validate input before processing it further.

How does improper neutralization of quoting syntax differ from other injection vulnerabilities?

It specifically involves mismanagement of quotes, whereas others might involve SQL or command injection.

What is the impact on business if this vulnerability is exploited?

Exploitation can lead to data corruption and unauthorized access, impacting financial and reputational aspects.

Vulnerabilities Related to Improper Neutralization of Quoting Syntax

| CWE | Name | Relationship | |—|—|—| | CWE-138 | Improper Neutralization of Special Elements (ChildOf) |

References

• MITRE
• 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 Improper Neutralization of Quoting Syntax and other risks before an attacker does.