static int cirrus_vga_read_gr(CirrusVGAState * s, unsigned reg_index)
{
    switch (reg_index) {
    case 0x00: // Standard VGA, BGCOLOR 0x000000ff
        return s->cirrus_shadow_gr0;
    case 0x01: // Standard VGA, FGCOLOR 0x000000ff
        return s->cirrus_shadow_gr1;
    case 0x02:			// Standard VGA
    case 0x03:			// Standard VGA
    case 0x04:			// Standard VGA
    case 0x06:			// Standard VGA
    case 0x07:			// Standard VGA
    case 0x08:			// Standard VGA
        return s->vga.gr[s->vga.gr_index];
    case 0x05:			// Standard VGA, Cirrus extended mode
    default:
	break;
    }

    if (reg_index < 0x3a) {
	return s->vga.gr[reg_index];
    } else {
#ifdef DEBUG_CIRRUS
	printf("cirrus: inport gr_index %02x\n", reg_index);
#endif
	return 0xff;
    }
}

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.