CWE-162: Improper Neutralization of Trailing Special Elements

What is Improper Neutralization of Trailing Special Elements?

• Overview: Improper Neutralization of Trailing Special Elements (CWE-162) occurs when an application receives input containing special characters or sequences at the end, which are not correctly sanitized or neutralized before being processed by another component. This can lead to unexpected behaviors or vulnerabilities in the downstream component.

• Exploitation Methods:

• Attackers can exploit this vulnerability by appending special characters or sequences to input data, which are then interpreted by the downstream component in unintended ways.
• Common attack patterns include injecting unexpected command terminators or escape sequences that alter the execution flow or modify data processing.

• Security Impact:

• Direct consequences of successful exploitation include unauthorized actions, data corruption, or even execution of arbitrary code.
• Potential cascading effects involve further exploitation of the application environment, leading to broader system compromise.
• Business impact can range from data breaches and loss of customer trust to financial loss and legal repercussions due to non-compliance with data protection regulations.

• Prevention Guidelines:

• Specific code-level fixes involve thoroughly sanitizing and validating all input data, especially focusing on trailing special characters or sequences.
• Security best practices include implementing input validation routines that check for and neutralize any special elements before passing data to downstream components.
• Recommended tools and frameworks include using established libraries and APIs for input validation and sanitization, as well as leveraging static analysis tools to identify potential weaknesses in code handling special elements.

Corgea can automatically detect and fix Improper Neutralization of Trailing Special Elements in your codebase. [Try Corgea free today](https://corgea.app).

Technical Details

Likelihood of Exploit: Not specified

Affected Languages: Not Language-Specific

Affected Technologies: Not specified

Vulnerable Code Example

Certainly! Below is the improved content with the necessary corrections and enhancements:

Python Example

def process_user_input(user_input):
    # Vulnerable: This code attempts to neutralize a trailing semicolon
    # but does not address other potentially dangerous trailing characters.
    if user_input.endswith(';'):
        user_input = user_input[:-1]  # Remove trailing semicolon
    
    # Further processing of user_input, which assumes no trailing special characters
    execute_command(f"echo {user_input}")

def execute_command(command):
    print(f"Executing command: {command}")

Explanation

In this vulnerable example, the code only removes a trailing semicolon from the user input. This could lead to security issues if other special characters are present, especially when the input is used in command execution. The assumption that no other special characters are present can be exploited.

How to fix Improper Neutralization of Trailing Special Elements?

To fix this vulnerability, it's essential to sanitize the input properly by removing or escaping hazardous characters. Here's how:

1. Remove or escape hazardous characters: Use a whitelist approach to allow only safe characters in user input.
2. Validate input: Ensure input matches a known safe pattern.
3. Use secure libraries: Prefer library functions that automatically handle escaping or neutralizing special characters.

Fixed Code Example

Python Example

import re

def process_user_input(user_input):
    # Fixed: Sanitize input by allowing only alphanumeric characters and spaces
    # This prevents any unexpected special character behavior.
    safe_input = re.sub(r'[^a-zA-Z0-9 ]', '', user_input)

    # Further processing of sanitized user_input
    execute_command(f"echo {safe_input}")

def execute_command(command):
    print(f"Executing command: {command}")

Explanation

In the fixed version, a regular expression is used to remove any characters that are not alphanumeric or spaces. This ensures that no special characters can influence the behavior of downstream components, particularly when constructing shell commands. This approach mitigates the risk of command injection or other unintended behavior caused by improper input neutralization.

By following these best practices, the code becomes more robust against security vulnerabilities related to improper neutralization of trailing special elements.