int check_dc_pred8x8_mode(int mode, int mb_x, int mb_y)
{
    if (!mb_x)
        return mb_y ? TOP_DC_PRED8x8 : DC_128_PRED8x8;
    else
        return mb_y ? mode : LEFT_DC_PRED8x8;
}

The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.