CWE-165: Improper Neutralization of Multiple Internal Special Elements

What is Improper Neutralization of Multiple Internal Special Elements?

• Overview: Improper Neutralization of Multiple Internal Special Elements (CWE-165) occurs when a software product receives input containing special characters or sequences that are not correctly sanitized or neutralized, allowing these elements to be interpreted in unintended ways when passed to another system component.

• Exploitation Methods:

• Attackers can exploit this vulnerability by injecting specially crafted input that includes multiple special elements, causing the receiving system to misinterpret or mishandle the input.
• Common attack patterns include SQL injection, command injection, or XML injection, where the special characters disrupt normal processing and can lead to unauthorized actions.

• Security Impact:

• Direct consequences of successful exploitation can include unauthorized access to data, execution of arbitrary code, or system crashes.
• Potential cascading effects might involve data breaches, privilege escalation, or compromise of interconnected systems.
• Business impact can be severe, leading to loss of customer trust, legal liabilities, and financial loss due to data breaches or service disruptions.

• Prevention Guidelines:

• Specific code-level fixes include using parameterized queries, prepared statements, and proper escaping functions to handle special elements securely.
• Security best practices involve validating and sanitizing all input, implementing input whitelisting, and adhering to the principle of least privilege.
• Recommended tools and frameworks include static analysis tools to detect improper handling of special elements and using libraries with built-in protections against injection vulnerabilities.

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Technical Details

Likelihood of Exploit: Not specified

Affected Languages: Not Language-Specific

Affected Technologies: Not specified

Vulnerable Code Example

import re

def process_user_input(user_input):
    # Vulnerability: The input is directly inserted into a SQL query
    # without proper sanitization, allowing SQL injection through special characters like ' or ".
    query = f"SELECT * FROM users WHERE username = '{user_input}'"  # Vulnerable line
    execute_query(query)

def execute_query(query):
    # Imagine this function executes the query against a database
    print(f"Executing: {query}")

# Example usage
process_user_input("admin' OR '1'='1")  # This input exploits the vulnerability

How to fix Improper Neutralization of Multiple Internal Special Elements?

The key issue here is the improper neutralization of special characters within the user input that can be interpreted in an unintended way by the SQL database. This is a classic example of SQL injection vulnerability. The best practice to fix this issue is to use parameterized queries or prepared statements, which ensure that user input is treated strictly as data and not executable code. This approach automatically escapes any special characters, preventing them from being misinterpreted by the SQL engine.

Fixed Code Example

import sqlite3

def process_user_input(user_input):
    # Fix: Use parameterized queries to safely incorporate user input
    with sqlite3.connect('example.db') as conn:
        cursor = conn.cursor()
        # Parameterized query: user_input is safely escaped
        query = "SELECT * FROM users WHERE username = ?"  # Secure line
        cursor.execute(query, (user_input,))  # User input is passed as a parameter
        results = cursor.fetchall()
        print(f"Results: {results}")

# Example usage
process_user_input("admin' OR '1'='1")  # This input is safely handled

In the fixed code example, we use sqlite3's execute method with a parameterized query. By using placeholders (e.g., ?) and passing the user input as a tuple, we ensure that the input is correctly escaped and treated as data, not as part of the SQL command. This eliminates the risk of SQL injection by neutralizing any potentially harmful special characters in the input.