static unsigned short readushort(FILE * f, int bigendian)
{
    unsigned char c1, c2;
    if (!fread(&c1, 1, 1, f)) {
        fprintf(stderr,
                "\nError: fread return a number of element different from the expected.\n");
        return 0;
    }
    if (!fread(&c2, 1, 1, f)) {
        fprintf(stderr,
                "\nError: fread return a number of element different from the expected.\n");
        return 0;
    }
    if (bigendian) {
        return (unsigned short)((c1 << 8) + c2);
    } else {
        return (unsigned short)((c2 << 8) + c1);
    }
}

The product writes data past the end, or before the beginning, of the intended buffer.