Disclaimer: Community trackers are created by Red Hat Product Security team on a best effort basis. Package maintainers are required to ascertain if the flaw indeed affects their package, before starting the update process.

In a query response, an attacker may send `named` multiple copies of a record that should only exist once (such as an SOA record). If the RDATA is the same on all the copies, the record is appended to the in-memory RDATA set, which can cause increased memory usage of the negative cache and possibly lead to other memory attack vectors.
This issue affects BIND 9 versions 9.11.0 through 9.18.50, 9.20.0 through 9.20.27, 9.21.0 through 9.21.25, 9.11.3-S1 through 9.18.50-S1, and 9.20.9-S1 through 9.20.27-S1.