Patched code sample

import builtins
import io
import sys

def execute_code(code: str) -> str:
    """
    Represents the fixed version of the code execution tool.
    The vulnerability is patched by wrapping the `print` function.
    """
    
    # This wrapper function does not have a `__self__` attribute that
    # points back to the `builtins` module, breaking the exploit chain.
    def safe_print_wrapper(*args, **kwargs):
        return builtins.print(*args, **kwargs)

    # The sandboxed environment's builtins are carefully selected.
    # The original `builtins.print` is replaced with the safe wrapper.
    safe_builtins = {
        'print': safe_print_wrapper,  # <-- THE FIX
        'vars': builtins.vars,
        'str': builtins.str,
        'int': builtins.int,
        'list': builtins.list,
        'dict': builtins.dict,
    }

    restricted_globals = {"__builtins__": safe_builtins}
    
    # Capture output to return as a string
    old_stdout = sys.stdout
    redirected_output = io.StringIO()
    sys.stdout = redirected_output
    
    try:
        # An attacker trying the payload would now get an AttributeError
        # because `safe_print_wrapper` does not have a `__self__` attribute.
        # Payload: "print(vars(print.__self__)['__import__']('os').system('echo pwned'))"
        exec(code, restricted_globals, {})
    except Exception as e:
        # The expected failure for the exploit is an AttributeError.
        print(f"Execution failed: {e}")
    finally:
        sys.stdout = old_stdout
        
    return redirected_output.getvalue()