ISC recently discovered an issue in BIND that allows TCP connection slots to be consumed for an indefinite time frame via a specifically crafted TCP stream sent from a client. This issue is present in BIND 9.16.11 to 9.16.26 (including S editions), and 9.18.0. This issue can only be triggered on BIND servers which have keep-response-order enabled, which is not the default configuration. The keep-response-order option is an ACL block; any hosts which are specified within it will be able to trigger this issue on affected versions. Specifically crafted TCP streams can cause connections to BIND to remain in CLOSE_WAIT status for an indefinite period of time, even after the client has terminated the connection.
ISC recently discovered an issue in BIND that allows TCP connection slots to be consumed for an indefinite time frame via a specifically crafted TCP stream sent from a client. This issue is present in BIND 9.16.11 to 9.16.26 (including S editions), and 9.18.0. This issue can only be triggered on BIND servers which have keep-response-order enabled, which is not the default configuration. The keep-response-order option is an ACL block; any hosts which are specified within it will be able to trigger this issue on affected versions. Specifically crafted TCP streams can cause connections to BIND to remain in CLOSE_WAIT status for an indefinite period of time, even after the client has terminated the connection.
Vulmon
Workarounds:
To mitigate this issue in all affected versions of BIND, use the default setting of keep-response-order { none; }.