What’s Vulnerable › Vulnerabilities

CVE-2026-67411: RabbitMQ: Web MQTT with PROXY Protocol enabled: a loopback-only user permission bypass

• Severity: high (CVSS 7.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2026-09-25 · updated 2026-10-08
• Weakness: CWE-863

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.

Affected products

• rabbitmq-server: from 3.13.0 before 3.13.18; from 4.0.0 before 4.0.23; from 4.1.0 before 4.1.14; from 4.2.0 before 4.2.9; from 4.3.0 before 4.3.3 — fixed in 3.13.18, 4.0.23, 4.1.14, 4.2.9, 4.3.3

How to fix

Upgrade to a fixed version: rabbitmq-server 3.13.18, 4.0.23, 4.1.14, 4.2.9. Check the vendor advisory for mitigations.

References

• https://github.com/rabbitmq/rabbitmq-server/commit/a7528314840c4f8dc9904684f9f97ffa7aac6349
• https://github.com/rabbitmq/rabbitmq-server/commit/edbead0eabbd65925d0dc914a22d6a29e155e646
• https://github.com/rabbitmq/rabbitmq-server/releases/tag/v4.2.9
• https://github.com/rabbitmq/rabbitmq-server/releases/tag/v4.3.3
• https://github.com/rabbitmq/rabbitmq-server/security/advisories/GHSA-4r6f-9cpw-f6g6
• https://github.com/rabbitmq/rabbitmq-server/security/advisories/GHSA-4r6f-9cpw-f6g6

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