Bug 2539766 (CVE-2026-66067)

Summary: CVE-2026-66067 rabbitmq: RabbitMQ: Authenticated user can bypass connection limits via stream protocol
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedKeywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in RabbitMQ. The stream protocol handler does not correctly enforce per-user and per-virtual host (vhost) connection limits. An authenticated user can exploit this by connecting through port 5552, bypassing the intended connection restrictions. This could lead to resource exhaustion and a denial of service (DoS) for the RabbitMQ broker.
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Description OSIDB Bzimport 2026-09-23 20:34:38 UTC 
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.