RabbitMQ is a messaging and streaming broker. From 3.13.0 until 4.3.3, 4.2.9 , 4.1.14, 4.0.24, and 3.13.18, Federation upstream in RabbitMQ skips vhost authorization allowing cross-vhost message access. what the bug lets you do. A policymaker on one vhost reads and drains messages out of another vhost it has no permission on. With the default ack-mode the source messages are consumed (deleted), not copied. Why that should not 1. Federation validates the upstream URI without any vhost-access Cross-vhost message read/drain from a per-vhost policymaker, breaking vhost tenancy This issue is fixed in versions 4.3.3, 4.2.9 , 4.1.14, 4.0.24, and 3.13.18.
https://github.com/rabbitmq/rabbitmq-server/security/advisories/GHSA-42pc-678q-v8qj
https://github.com/rabbitmq/rabbitmq-server/releases/tag/v4.3.3
https://github.com/rabbitmq/rabbitmq-server/releases/tag/v4.2.9
Published: 2026-09-25
Updated: 2026-09-25
Base Score: 4
Vector: CVSS2#AV:N/AC:L/Au:S/C:P/I:N/A:N
Severity: Medium
Base Score: 7.5
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Severity: High
Base Score: 6
Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:N/VA:N/SC:L/SI:N/SA:N
Severity: Medium
EPSS: 0.00302