A malicious client can send many DNS messages over TCP, potentially causing the server to become unstable while the attack is in progress. The server may recover after the attack ceases. Use of ACLs will not mitigate the attack. This issue affects BIND 9 versions 9.18.1 through 9.18.27, 9.19.0 through 9.19.24, and 9.18.11-S1 through 9.18.27-S1.
CWE-770 Allocation of Resources Without Limits or Throttling