Patched code sample

import subprocess
import re

def fixed_update_device_setting(key: str, value: str):
    """
    Safely updates a device setting by validating the input value and using
    subprocess with an argument list to prevent command injection.
    """
    # 1. Validate the input using a whitelist. Here, we only allow a safe
    # subset of characters commonly found in hostnames or IP addresses.
    if not re.match(r'^[a-zA-Z0-9.\-_]+$', value):
        # In a real application, this would log the attempt and return an error.
        return

    # 2. Use subprocess.run() with a list of arguments. The 'value' is passed
    # as a distinct argument and is not interpreted by the shell, which
    # prevents command injection.
    command = ["/usr/sbin/nvram_set", key, value]

    try:
        # The 'check=True' argument will raise an exception if the command
        # returns a non-zero exit code (indicating an error).
        subprocess.run(command, check=True, capture_output=True)
    except (FileNotFoundError, subprocess.CalledProcessError) as e:
        # Handle cases where the command doesn't exist or fails.
        # In a real application, this would be logged.
        pass