RabbitMQ: Web MQTT with PROXY Protocol enabled: a loopback-only user permission bypass
CVE-2026-67411 is fixed in rabbitmq-server on 1 platform by DEBIAN-CVE-2026-67411 (version 4.3.6-1), released October 10, 2026. It is not reported as exploited. Patch Radar priority: High.
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.
Where it's fixed
| Product | Fixed in | Fix | Released |
|---|---|---|---|
| Linux | |||
| rabbitmq-server · Debian 14 | 4.3.6-1 | DEBIAN-CVE-2026-67411 | Oct 10, 2026 |
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