| Description: | Every `named` instance configured to run as a recursive resolver
maintains a cache database holding the responses to the queries it has
recently sent to authoritative servers. The size limit for that cache
database can be configured 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, a cache-cleaning algorithm starts to remove expired
and/or least-recently used RRsets from the cache, to keep memory use
below the configured limit. It has been discovered that the
effectiveness of the cache-cleaning algorithm used in `named` can be
severely diminished by querying the resolver for specific RRsets in a
certain order, effectively allowing the configured `max-cache-size`
limit to be significantly exceeded. This issue affects BIND 9 versions
9.11.0 through 9.16.41, 9.18.0 through 9.18.15, 9.19.0 through
9.19.13, 9.11.3-S1 through 9.16.41-S1, and 9.18.11-S1 through
9.18.15-S1.
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