CVE-2023-2828: named's configured cache size limit can be significantly exceeded

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.

— Red Hat

ISC BIND is vulnerable to a denial of service, caused by a flaw that allows the named's configured cache size limit to be significantly exceeded. By querying the resolver for specific RRsets in a certain order, a remote attacker could exploit this vulnerability to exhaust all memory on the host.

— IBM