CoreFocusEvent(DeviceIntPtr dev, int type, int mode, int detail, WindowPtr pWin)
{
    xEvent event = {
        .u.u.type = type,
        .u.u.detail = detail
    };
    event.u.focus.mode = mode;
    event.u.focus.window = pWin->drawable.id;

    DeliverEventsToWindow(dev, pWin, &event, 1,
                          GetEventFilter(dev, &event), NullGrab);
    if ((type == FocusIn) &&
        ((pWin->eventMask | wOtherEventMasks(pWin)) & KeymapStateMask)) {
        xKeymapEvent ke = {
            .type = KeymapNotify
        };
        ClientPtr client = wClient(pWin);
        int rc;

        rc = XaceHook(XACE_DEVICE_ACCESS, client, dev, DixReadAccess);
        if (rc == Success)
            memcpy((char *) &ke.map[0], (char *) &dev->key->down[1], 31);

        DeliverEventsToWindow(dev, pWin, (xEvent *) &ke, 1,
                              KeymapStateMask, NullGrab);
    }
}

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.