High severity · published Sep 25, 2026
CVE-2026-67411
RabbitMQ: Web MQTT with PROXY Protocol enabled: a loopback-only user permission bypass
7.1
CVSS
0.3%
EPSS
No
On KEV
Description
RabbitMQ is a messaging and streaming broker. From 3.13.0 until 3.13.18, 4.0.23, 4.1.14, 4.2.9, and 4.3.3, native MQTT and MQTT over WebSocket behind a trusted PROXY Protocol frontend could lose the proxy-derived client address before the MQTT authentication path checked loopback_users, causing the frontend-to-broker address to be treated as loopback. An attacker who can reach the trusted frontend and has valid credentials for a loopback-restricted account can therefore bypass the source-address restriction; the issue does not bypass password authentication. This issue is fixed in versions 3.13.18, 4.0.23, 4.1.14, 4.2.9, and 4.3.3.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
None
Confidentiality
High
Integrity
Low
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.3% · higher than 25% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
RA
rabbitmq-server · rabbitmq
>= 4.3.0, < 4.3.3; >= 4.2.0, < 4.2.9; >= 4.1.0, < 4.1.14; >= 4.0.0, < 4.0.23; >= 3.13.0, < 3.13.18 · source: vendor
RS
Rabbitmq Server · Broadcom
3.13.0 before 3.13.18; 4.0.0 before 4.0.23; 4.1.0 before 4.1.14; 4.2.0 before 4.2.9; 4.3.0 before 4.3.3 · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-67411
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-67411
Patch
https://github.com/rabbitmq/rabbitmq-server/commit/a7528314840c4f8dc9904684f9f97ffa7aac6349
Patch
https://github.com/rabbitmq/rabbitmq-server/commit/edbead0eabbd65925d0dc914a22d6a29e155e646
Release Notes
https://github.com/rabbitmq/rabbitmq-server/releases/tag/v4.2.9
Release Notes
https://github.com/rabbitmq/rabbitmq-server/releases/tag/v4.3.3
Exploit
https://github.com/rabbitmq/rabbitmq-server/security/advisories/GHSA-4r6f-9cpw-f6g6
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