CWE-198: Use of Incorrect Byte Ordering

What is Use of Incorrect Byte Ordering?

• Overview: Use of Incorrect Byte Ordering occurs when a program fails to correctly handle the byte order of data received from another system, leading to the misinterpretation of numerical values. This often happens due to differences in endian formats, such as big-endian and little-endian.

• Exploitation Methods:

• Attackers can exploit this vulnerability by sending data with a byte order that the system does not expect, causing incorrect calculations or data interpretation.
• Common attack patterns include data injection with manipulated byte order and exploiting assumptions in data processing functions.

• Security Impact:

• Direct consequences of successful exploitation include incorrect program behavior, data corruption, and faulty computations.
• Potential cascading effects involve triggering further vulnerabilities due to incorrect data handling, like buffer overflows or logic errors.
• Business impact can include system crashes, data loss, and incorrect business decisions based on faulty data.

• Prevention Guidelines:

• Specific code-level fixes include explicitly specifying the expected byte order when reading and writing data, using functions that handle endian conversion.
• Security best practices involve thorough input validation, testing for different endian scenarios, and awareness of platform-specific data handling.
• Recommended tools and frameworks are those that abstract byte order handling, such as network libraries and serialization frameworks that automatically manage endian differences.

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Technical Details

Likelihood of Exploit: Not specified

Affected Languages: Not Language-Specific

Affected Technologies: Not specified

Vulnerable Code Example

Here is the improved content for the code examples demonstrating CWE-198 (Use of Incorrect Byte Ordering):

Python Example

import struct

def process_data(data):
    # Vulnerable code: Incorrectly assumes data is in big-endian format
    # This can lead to misinterpretation of data if it is actually little-endian
    value = struct.unpack('>I', data)[0]
    print(f"Processed value: {value}")

# Example usage
data = b'\x01\x00\x00\x00'  # Expected to be little-endian, but processed as big-endian
process_data(data)  # Incorrect value will be printed

In this vulnerable code, the process_data function uses a hardcoded big-endian format specifier ('>I') to unpack the data. This can result in incorrect interpretation if the data is actually in little-endian format.

How to fix Use of Incorrect Byte Ordering?

Fixed Code Example

import struct

def process_data(data, byte_order):
    # Fixed code: Correctly processes data based on specified byte order
    if byte_order == 'big':
        format_char = '>'
    elif byte_order == 'little':
        format_char = '<'
    else:
        raise ValueError("Invalid byte order specified")

    value = struct.unpack(f'{format_char}I', data)[0]
    print(f"Processed value: {value}")

# Example usage
data = b'\x01\x00\x00\x00'  # Little-endian format
process_data(data, 'little')  # Correct value will be printed

In the fixed code, a byte_order parameter is added to the process_data function, allowing the caller to specify the correct byte order. This ensures the data is unpacked correctly, preventing misinterpretation due to incorrect assumptions about the byte order.

Key Improvements:

• Correct syntax highlighting and line number formatting.
• Clear explanation of the vulnerability and how to fix it.
• Realistic and clear demonstration of the issue and its resolution.
• Adherence to Python best practices and improved code readability.