We recently found a security issue in our HBase REST servers. The issue is a variant of the POODLE vulnerability (https://en.wikipedia.org/wiki/POODLE) and is present in the HBase Thrift server as well. It also appears to affect the JMXListener coprocessor. The vulnerabilities probably affect all versions of HBase that have the affected services. (If you don't use the affected services with SSL then this ticket probably doesn't affect you).
Included is a patch to fix the known POODLE vulnerabilities in master. Let us know if we missed any. From our end we only personally encountered the HBase REST vulnerability. We do not use the Thrift server or JMXListener coprocessor but discovered those problems after discussing the issue with some of the HBase PMCs.
Coincidentally, Hadoop recently committed a SslSelectChannelConnectorSecure which is more or less the same as one of the fixes in this patch. Hadoop wasn't originally affected by the vulnerability in the SslSelectChannelConnector, but about a month ago they committed
HADOOP-12765 which does use that class, so they added a SslSelectChannelConnectorSecure class similar to this patch. Since this class is present in Hadoop 2.7.4+ which hasn't been released yet, we will for now just include our own version instead of depending on the Hadoop version.
After the patch is approved for master we can backport as necessary to older versions of HBase.