GHSA-cqgj-h8vf-4w59 Acknowledgement extension out of memory

• Maven org.cometd.java:cometd-java-server-common: >= 5.0.0, < 5.0.23 → fixed in 5.0.23 • Maven org.cometd.java:cometd-java-server-common: >= 6.0.0, < 6.0.19 → fixed in 6.0.19 • Maven org.cometd.java:cometd-java-server-common: >= 7.0.0, < 7.0.19 → fixed in 7.0.19 • Maven org.cometd.java:cometd-java-server-common: >= 8.0.0, < 8.0.9 → fixed in 8.0.9

Impact Bad clients that always send a fixed batch value while the server is using the acknowledgement extension can cause the unacknowledged message queue to grow indefinitely, eventually resulting in an OutOfMemoryError. Such bad clients would always send: ```json { "channel": "/meta/connect", ... "ext": { "ack": 1 } } ``` The server would never clear the unacknowledged message queue, and one bad client can cause a server outage. Patches 5.0.x - https://github.com/cometd/cometd/pull/2168 6.0.x - https://github.com/cometd/cometd/pull/2169 8.0.x - https://github.com/cometd/cometd/pull/2118 Workarounds Disable the acknowledgement extension. Resources https://github.com/cometd/cometd/discussions/2116 https://github.com/cometd/cometd/issues/2117