Vulnerability · Published Sep 23, 2026 · Assigned by GitHub_M

CVE-2026-66067RabbitMQ: Stream protocol skips per vhost per user connection limits

Medium 6.0

In plain English

A medium-severity resource allocation without limits in rabbitmq-server from rabbitmq. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 38% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 4.0)6.0Medium

Exploit odds (30 days)0.4%top 61.8% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official description

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.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
Debian:14	rabbitmq-server	4.3.2-1	DEBIAN-CVE-2026-66067
Ubuntu:22.04:LTS	rabbitmq-server	no fix listed	UBUNTU-CVE-2026-66067
Ubuntu:24.04:LTS	rabbitmq-server	no fix listed	UBUNTU-CVE-2026-66067
Ubuntu:26.04:LTS	rabbitmq-server	no fix listed	UBUNTU-CVE-2026-66067

Affected products (as reported)

Vendor	Product	Versions
rabbitmq	rabbitmq-server	>= 4.2.0, < 4.2.7>= 4.3.0, < 4.3.1

Weakness: CWE-770 · Vector: 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

References

https://github.com/rabbitmq/rabbitmq-server/security/advisories/GHSA-hwqx-2gfg-89qf x_refsource_CONFIRM
https://github.com/rabbitmq/rabbitmq-server/releases/tag/v4.2.7 x_refsource_MISC
https://github.com/rabbitmq/rabbitmq-server/releases/tag/v4.3.1 x_refsource_MISC