#fixed code
                                @Override
    public void parse(NulsByteBuffer buffer) throws NulsException {
        magicNumber = buffer.readUint32();
        severPort = buffer.readUint16();
        port = severPort;
        ip = buffer.readString();
        this.groupSet = ConcurrentHashMap.newKeySet();
    }
#vulnerable code 
                                @Override
    public void parse(NulsByteBuffer buffer) throws NulsException {
        magicNumber = (int) buffer.readVarInt();
        severPort = (int) buffer.readVarInt();
        port = severPort;
        ip = new String(buffer.readByLengthByte());
        this.groupSet = ConcurrentHashMap.newKeySet();
    } 
                            #location 6 
                            #vulnerability type NULL_DEREFERENCE