Affected: ISC BIND 9

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.

Affected: Ubuntu:20.04:LTS: bind9, Ubuntu:22.04:LTS: bind9

Shoham Danino, Anat Bremler-Barr, Yehuda Afek, and Yuval Shavitt discovered that Bind incorrectly handled the cache size limit. A remote attacker could possibly use this issue to consume memory, leading to a denial of service. (CVE-2023-2828)

It was discovered that Bind incorrectly handled the recursive-clients quota. A remote attacker could possibly use this issue to cause Bind to crash, resulting in a denial of service. This issue only affected Ubuntu 22.04 LTS, Ubuntu 22.10, and Ubuntu 23.04. (CVE-2023-2911)