CVE-2026-66067

RabbitMQ is a messaging and streaming broker. Prior to versions 4.2.7 and 4.3.1, The stream open handler calls only check_vhost_access; it omits the node/vhost/user connection-limit checks that rabbit_reader performs for AMQP. A developer %% FIXME comment at the cited line explicitly acknowledges the gap. No compensating enforcement exists in connection tracking or elsewhere in rabbitmq_stream. An authenticated tenant can fully bypass operator-configured per-user and per-vhost connection caps by connecting via port 5552 instead of 5672. Preconditions include rabbitmq_stream plugin enabled Authenticated stream-protocol credentials Operator relies on per-user/per-vhost connection limits for tenant isolation. This issue is fixed in versions 4.2.7 and 4.3.1.

• https://github.com/rabbitmq/rabbitmq-server/releases/tag/v4.2.7Release Notes
• https://github.com/rabbitmq/rabbitmq-server/releases/tag/v4.3.1Release Notes
• https://github.com/rabbitmq/rabbitmq-server/security/advisories/GHSA-hwqx-2gfg-89qfVendor Advisory