#fixed code
                                @Override
    public NetworkEventResult process(BaseEvent networkEvent, Node node) {
        VersionEvent event = (VersionEvent) networkEvent;

//        String key = event.getHeader().getEventType() + "-" + node.getId();
//        if (cacheService.existEvent(key)) {
//            Log.info("----------VersionEventHandler  cacheService  existEvent--------");
//            getNetworkService().removeNode(node.getId());
//            return null;
//        }
//        cacheService.putEvent(key, event, true);

        if (event.getBestBlockHeight() < 0) {
            throw new NetworkMessageException(ErrorCode.NET_MESSAGE_ERROR);
        }
        node.setVersionMessage(event);

        if (!node.isHandShake()) {
            node.setStatus(Node.HANDSHAKE);
            node.setPort(event.getExternalPort());
            node.setLastTime(TimeService.currentTimeMillis());
            getNodeDao().saveChange(NodeTransferTool.toPojo(node));
        }
        return null;
    }
#vulnerable code 
                                @Override
    public NetworkEventResult process(BaseEvent networkEvent, Node node) {
        VersionEvent event = (VersionEvent) networkEvent;

        String key = event.getHeader().getEventType() + "-" + node.getId();
        if (cacheService.existEvent(key)) {
            Log.info("----------VersionEventHandler  cacheService  existEvent--------");
            getNetworkService().removeNode(node.getId());
            return null;
        }
        cacheService.putEvent(key, event, true);

        if (event.getBestBlockHeight() < 0) {
            throw new NetworkMessageException(ErrorCode.NET_MESSAGE_ERROR);
        }
        node.setVersionMessage(event);

        if (!node.isHandShake()) {
            node.setStatus(Node.HANDSHAKE);
            node.setPort(event.getExternalPort());
            node.setLastTime(TimeService.currentTimeMillis());
            getNodeDao().saveChange(NodeTransferTool.toPojo(node));
        }
        return null;
    } 
                            #location 8 
                            #vulnerability type NULL_DEREFERENCE