void pcnet_ioport_writew(void *opaque, uint32_t addr, uint32_t val)
{
    PCNetState *s = opaque;
    pcnet_poll_timer(s);
#ifdef PCNET_DEBUG_IO
    printf("pcnet_ioport_writew addr=0x%08x val=0x%04x\n", addr, val);
#endif
    if (!BCR_DWIO(s)) {
        switch (addr & 0x0f) {
        case 0x00: /* RDP */
            pcnet_csr_writew(s, s->rap, val);
            break;
        case 0x02:
            s->rap = val & 0x7f;
            break;
        case 0x06:
            pcnet_bcr_writew(s, s->rap, val);
            break;
        }
    }
    pcnet_update_irq(s);
}

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.