In Apache NiFi 1.2.0 to 1.11.4, the NiFi UI and API were protected by mandating TLS v1.2, as well as listening connections established by processors like ListenHTTP, HandleHttpRequest, etc. However intracluster communication such as cluster request replication, Site-to-Site, and load balanced queues continued to support TLS v1.0 or v1.1.
github.com/apache/nifi
github.com/apache/nifi/commit/441781cec50f77d9f1e65093f55bbd614b8c5ec6
lists.apache.org/thread.html/r2d9c21f9ec35d66f2bb42f8abe876dabd786166b6284e9a33582c718@%3Ccommits.nifi.apache.org%3E
lists.apache.org/thread.html/re48582efe2ac973f8cff55c8b346825cb491c71935e15ab2d61ef3bf@%3Ccommits.nifi.apache.org%3E
nifi.apache.org/security#CVE-2020-9491
nvd.nist.gov/vuln/detail/CVE-2020-9491