- CVE-2023-6516: bound the memory used to queue RBTDB tree-pruning events, so that recursive query patterns which continuously trigger cache-database maintenance can no longer exceed max-cache-size and exhaust host memory (DoS) - CVE-2023-6516 follow-up: make the tree-pruning queue per-node-lock bucketed and process it in quanta, so that the queue introduced above does not starve cache cleanup under load and let cache memory grow without bound - CVE-2023-6516 follow-up: handle a node being re-queued for tree pruning gracefully instead of asserting, and do not append a parent to a pruning list it is already on, avoiding an assertion failure (DoS) and pruning-list corruption reachable through normal cache activity - CVE-2023-6516 follow-up: adopt the pruning design upstream settled on in 9.16.49 - run tree pruning on a dedicated task with an unlimited quantum instead of sharing the quantum-1 cache database task, clean every eligible ancestor in a single pass, and re-create both tasks when the cache is flushed so that pruning keeps working after "rndc flush"