bind9: Every `named` instance configured to run as a recursive resolver maintainsa cache database holding the responses to t...

Every `named` instance configured to run as a recursive resolver maintainsa cache database holding the responses to the queries it has recently sentto authoritative servers. The size limit for that cache database can beconfigured using the `max-cache-size` statement in the configuration file;it defaults to 90% of the total amount of memory available on the host.When the size of the cache reaches 7/8 of the configured limit, acache-cleaning algorithm starts to remove expired and/or least-recentlyused RRsets from the cache, to keep memory use below the configured limit.It has been discovered that the effectiveness of the cache-cleaningalgorithm used in `named` can be severely diminished by querying theresolver for specific RRsets in a certain order, effectively allowing theconfigured `max-cache-size` limit to be significantly exceeded.This issue affects BIND 9 versions 9.11.0 through 9.16.41, 9.18.0 through9.18.15, 9.19.0 through 9.19.13, 9.11.3-S1 through 9.16.41-S1, and9.18.11-S1 through 9.18.15-S1.

Where it's fixed