Setting vector elements in range-based for loop

I have come across what I consider weird behaviour with the c++11 range-based for loop when assigning to elements of a dynamically allocated std::vector. I have the following code:

int arraySize = 1000;
std::string fname = "aFileWithLoadsOfNumbers.bin";
CTdata = new std::vector<short int>(arraySize, 0);
std::ifstream dataInput(fname.c_str(), std::ios::binary);
if(dataInput.is_open()
{
    std::cout << "File opened sucessfully" << std::endl;
    for(auto n: *CTdata)
    {
        dataInput.read(reinterpret_cast<char*>(&n), sizeof(short int));
        // If I do "cout << n << endl;" here, I get sensible results   
    }
    // However, if I do something like "cout << CTdata->at(500) << endl;" here, I get 0
}
else
{
    std::cerr << "Failed to open file." << std::endl;
}

If I change the loop to a more traditional for(int i=0; i<arraySize; i++) and use &CTdata->at(i) in place of &n in the read function, things do as I would expect.

What am I missing?