Two four letter word commands “wchp/wchc” are CPU intensive and could cause spike of CPU utilization on Apache ZooKeeper server if abused, which leads to the server unable to serve legitimate client requests. Apache ZooKeeper thru version 3.4.9 and 3.5.2 suffer from this issue, fixed in 3.4.10, 3.5.3, and later.
www.debian.org/security/2017/dsa-3871
www.securityfocus.com/bid/98814
access.redhat.com/errata/RHSA-2017:2477
access.redhat.com/errata/RHSA-2017:3354
access.redhat.com/errata/RHSA-2017:3355
issues.apache.org/jira/browse/ZOOKEEPER-2693
lists.apache.org/thread.html/053d9ce4d579b02203db18545fee5e33f35f2932885459b74d1e4272@%3Cissues.activemq.apache.org%3E
lists.apache.org/thread.html/58170aeb7a681d462b7fa31cae81110cbb749d2dc83c5736a0bb8370@%3Cdev.zookeeper.apache.org%3E
lists.apache.org/thread.html/bcce5a9c532b386c68dab2f6b3ce8b0cc9b950ec551766e76391caa3@%3Ccommits.nifi.apache.org%3E
lists.apache.org/thread.html/rca37935d661f4689cb4119f1b3b224413b22be161b678e6e6ce0c69b@%3Ccommits.nifi.apache.org%3E
nvd.nist.gov/vuln/detail/CVE-2017-5637
www.oracle.com//security-alerts/cpujul2021.html
www.oracle.com/security-alerts/cpujul2020.html