Executive brief
RabbitMQ is a widely used messaging broker that facilitates communication between different software applications. A security flaw in how it handles certain network protocols could allow restricted users, such as the default 'guest' account, to connect to the server remotely even when they are supposed to be limited to local access only. This could lead to unauthorized access to sensitive message data if the server is configured to trust certain network proxy traffic.
Technical details
An authentication bypass vulnerability exists in RabbitMQ's handling of AMQP 0-9-1, AMQP 1.0, and Stream Protocol connections. The root cause is an incorrect loopback check that utilizes the listener-side socket address (sockname) instead of the actual client source address (peername) when traffic is received through a trusted PROXY-protocol path. This allows users restricted to loopback interfaces (like the default 'guest' user) to bypass these restrictions and connect from remote network locations. The vulnerability is present when the backend listener is bound to a loopback address but receives proxied traffic. It has been addressed by updating the check to use the correct peer identity.
Affected products
- RabbitMQ RabbitMQ Server >= 3.13.0, < 3.13.15; >= 4.0.0, < 4.0.21; >= 4.1.0, < 4.1.11; >= 4.2.0, < 4.2.6
Timeline
- 2026-07-10: advisory: NVD publication date
- 2026-04-06: patched: Fix merged into main branch
References
- https://github.com/rabbitmq/rabbitmq-server/commit/7273c9eb6920abcde17b892dbe97ccaf906ead47
- https://github.com/rabbitmq/rabbitmq-server/commit/9f8c39fcf0acbc43080ee7017a62a02832114112
- https://github.com/rabbitmq/rabbitmq-server/pull/15936
- https://github.com/rabbitmq/rabbitmq-server/pull/15940
- https://github.com/rabbitmq/rabbitmq-server/releases/tag/v4.2.6
- https://github.com/rabbitmq/rabbitmq-server/security/advisories/GHSA-36m6-588r-vqcw