---
id: CVE-2026-66067
title: RabbitMQ is a messaging and streaming broker
summary: >-
  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 develope…
severity: medium
cvss: 6
cvssVector: 'CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N'
cwe:
  - CWE-770
  - CWE-1220
vendor: rabbitmq
product: rabbitmq-server
affected:
  - 'rabbitmq-server >= 4.2.0, < 4.2.7'
  - 'rabbitmq-server >= 4.3.0, < 4.3.1'
published: '2026-09-23'
updated: '2026-09-23'
sourceUpdated: '2026-09-23T21:16:58.783'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-66067'
references:
  - url: 'https://github.com/rabbitmq/rabbitmq-server/releases/tag/v4.2.7'
    label: security-advisories@github.com
  - url: 'https://github.com/rabbitmq/rabbitmq-server/releases/tag/v4.3.1'
    label: security-advisories@github.com
  - url: >-
      https://github.com/rabbitmq/rabbitmq-server/security/advisories/GHSA-hwqx-2gfg-89qf
    label: security-advisories@github.com
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-66067.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-66067'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2539766'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-66067'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-66067'
  - url: 'https://access.redhat.com/errata/RHSA-2026:67552'
tags:
  - nvd
  - cve.org
  - csaf
  - vex
  - red-hat
cvssSource: cna
ingestedAt: '2026-09-23T20:32:10.760Z'
patched:
  - hardened_images
scores:
  cna: 6
  vendor: 6.5
---

## Overview

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.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

## Vendor advisories

- **RHSA-2026:67552** · Red Hat · fixed in: Red Hat Hardened Images · released 2026-09-15 · [advisory](https://access.redhat.com/errata/RHSA-2026:67552)
- **Red Hat VEX** · Moderate · affected: Red Hat Hardened Images · no fix planned: Red Hat Hardened Images · updated 2026-09-24 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-66067.json)