CWE-1284: Improper Validation of Specified Quantity in Input

What is Improper Validation of Specified Quantity in Input?

• Overview: This vulnerability occurs when a program receives input that is supposed to define a quantity (like size, length, or time) and fails to properly validate these values. This can lead to incorrect assumptions about resource needs or operational limits.

• Exploitation Methods:

• Attackers can input excessively large or small quantities to cause resource exhaustion or unexpected behavior.
• Common attack patterns include causing buffer overflows by specifying oversized quantities or triggering denial of service through excessive resource consumption.

• Security Impact:

• Direct consequences include application crashes, data corruption, or denial of service.
• Potential cascading effects involve broader system instability or security breaches.
• Business impact may include service downtime, loss of customer trust, and financial losses due to operational disruptions.

• Prevention Guidelines:

• Implement strict input validation to ensure quantities are within acceptable ranges.
• Use built-in language features or libraries that handle input validation securely.
• Employ tools and frameworks that support input validation and provide protection against common vulnerabilities.

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Technical Details

Likelihood of Exploit: Not specified

Affected Languages: Not Language-Specific

Affected Technologies: Not specified

Vulnerable Code Example

Python Example

def add_to_cart(cart, product_id, quantity):
    # This function adds a specified quantity of a product to the shopping cart
    # Vulnerability: The function does not validate the quantity parameter properly
    cart.append({"product_id": product_id, "quantity": quantity})
    
cart = []
add_to_cart(cart, "123", 10000)  # Example call with excessive quantity

Issues in the Vulnerable Code:

• Lack of Validation: There is no check to ensure that quantity is a positive integer and within a reasonable range. This can lead to inventory abuse or potential Denial of Service (DoS) attacks by allowing excessively large quantities.
• No Error Handling: The function does not provide feedback when invalid input is given, making it difficult to diagnose issues.

How to fix Improper Validation of Specified Quantity in Input?

To fix this vulnerability, the function should:

1. Validate Input Type and Range: Ensure the quantity is a positive integer and does not exceed a predefined maximum limit.
2. Implement Error Handling: Provide clear feedback for invalid inputs, which helps in debugging and maintaining system integrity.

Fixed Code Example

Python Example

def add_to_cart(cart, product_id, quantity):
    # Validate that quantity is a positive integer and does not exceed a specified limit
    if not isinstance(quantity, int) or quantity <= 0:
        raise ValueError("Quantity must be a positive integer.")

    MAX_QUANTITY = 100  # Set a reasonable upper limit to prevent abuse
    if quantity > MAX_QUANTITY:
        raise ValueError(f"Quantity cannot exceed {MAX_QUANTITY}.")

    cart.append({"product_id": product_id, "quantity": quantity})

cart = []
try:
    add_to_cart(cart, "123", 10000)  # Example call with excessive quantity
except ValueError as e:
    print(f"Error: {e}")  # Handle the error gracefully

Improvements in the Fixed Code:

• Input Validation: The code now checks if quantity is a positive integer and does not exceed MAX_QUANTITY, preventing misuse.
• Error Handling: The function raises a ValueError with descriptive messages when invalid input is detected, which is caught and handled gracefully in the calling code.
• Documentation: Comments clearly explain the validation logic and the purpose of the MAX_QUANTITY limit, enhancing code readability and maintainability.