#vulnerable code 
                                @Override
    public List<Transaction> getWaitingTxList() throws NulsException {
        List<TransactionLocalPo> poList = localTxDao.getUnConfirmTxs();
        List<Transaction> txList = new ArrayList<>();
        for (TransactionLocalPo po : poList) {
            Transaction tx = UtxoTransferTool.toTransaction(po);
            txList.add(tx);
        }
        return txList;
    } 
                            #location 6 
                            #vulnerability type THREAD_SAFETY_VIOLATION
#fixed code
                                @Override
    public List<Transaction> getWaitingTxList() throws NulsException {
        return ledgerCacheService.getUnconfirmTxList();
    }