I just ran into the same thing while running Django locally with the runserver command. Besides the setuid request, there were several other requests at the same time;
code 400, message Bad request version ('\x9fX\x89\x88ã')
code 400, message Bad request version ('·ü\x19.\x9f]\x00\x12\x00\x00ÿ\x01\x00\x01\x00\x00#\x00\x00\x00\x05\x00\x05\x01\x00\x00\x00\x00\x00+\x00\x07\x06ÚÚ\x03\x04\x03\x03\x00')
code 400, message Bad request version ('û5')
code 400, message Bad request version ('\x00\x12\x00\x10\x04\x03\x08\x04\x04\x01\x05\x03\x08\x05\x05\x01\x08\x06\x06\x01\x00+\x00\x07\x06ºº\x03\x04\x03\x03ÿ\x01\x00\x01\x00\x00#\x00\x00\x00')
Notice that what appear in the apparently binary strings are non-octal characters, presumably because that allows some exploit on parsing.
code 400, message Bad request version ('\x9fX\x89\x88ã') code 400, message Bad request version ('·ü\x19.\x9f]\x00\x12\x00\x00ÿ\x01\x00\x01\x00\x00#\x00\x00\x00\x05\x00\x05\x01\x00\x00\x00\x00\x00+\x00\x07\x06ÚÚ\x03\x04\x03\x03\x00') code 400, message Bad request version ('û5') code 400, message Bad request version ('\x00\x12\x00\x10\x04\x03\x08\x04\x04\x01\x05\x03\x08\x05\x05\x01\x08\x06\x06\x01\x00+\x00\x07\x06ºº\x03\x04\x03\x03ÿ\x01\x00\x01\x00\x00#\x00\x00\x00')
Notice that what appear in the apparently binary strings are non-octal characters, presumably because that allows some exploit on parsing.