There is variable currentSize marked with modifier as volatile, what hint variable currentSize is used in multithreaded manner, as volatile ensures actual value can be seen between threads.
On the other side there is update operation on currentSize, which is not written in atomic manner, so can lead race condition.

    @Override
    protected void write(byte[] bytes) throws IOException {
        super.write(bytes);
        currentSize += bytes.length;
    }

Setting as Critical as that can lead to strange / hard to reproduce errors.
https://scan7.coverity.com/reports.htm#v23632/p11778/fileInstanceId=15443553&defectInstanceId=3634186&mergedDefectId=1429223