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v2.12.7Networking & Messaging

Apr 15, 2026Copy link

v2.12.7 is a targeted bug-fix release addressing ACL bypass vulnerabilities, multiple leafnode panics, a JetStream consumer stuck state, and an MQTT JWT regression from 2.12.6.

• securityPatch ACL bypass bugs immediately if you use deny rules or queue groups

  Two ACL enforcement bugs are fixed here. Overlapping wildcard patterns in deny ACLs were not enforced correctly, and queue subscriptions could bypass non-queue deny rules entirely. If your security model relies on deny-based ACLs — especially with wildcards or mixed queue/non-queue subscribers — treat this as a must-upgrade. Audit your ACL configurations after upgrading to confirm expected deny behavior is active.

• breakingMQTT users on 2.12.6 must upgrade — auth callout JWT was broken

  If you deployed 2.12.6 with MQTT clients using auth callout, JWTs were not being forwarded to the callout service, meaning your auth logic was silently bypassed or failing. This regression is fixed in 2.12.7. Upgrade immediately and verify MQTT client authentication is functioning end-to-end.

• enhancementmax_mem_store and max_file_store can now be increased via config reload

  You can now raise JetStream storage limits without restarting the server — just update the config and reload. Decreasing is still not supported via reload. Useful for capacity adjustments during peak periods without downtime. Plan your storage sizing with headroom so you can expand reactively if needed.