CVE-2026-67421RabbitMQ is a messaging and streaming broker. From 3.13.0 until 3.13.19, 4.0.24, 4.1.15, 4.2.10, and 4.3.5, RabbitMQ Management rendered an AMQP authorization-error reason containing an attacker-controlled queue name as HTML when the OAuth management UI was enabled. Exploitation requires an attacker with queue configure permission, a management administrator who can see but cannot read that queue, and the administrator clicking Get Message(s). A queue name containing a base element can then retarget the automatic relative refresh because the Content Security Policy omits base-uri and connect-src, and an attacker endpoint that permits the management origin through CORS can receive the victim's Authorization header. This issue is fixed in versions 3.13.19, 4.0.24, 4.1.15, 4.2.10, and 4.3.5.