High · published September 25, 2026
RabbitMQ is a messaging and streaming broker. From 4.0.0 until 4.3.3 and 4.2.9 and 4.1.14 and 4.0.23, Incomplete fix for CVE-2026-44838: escaperegexchar/1 does not escape -, leaving room for an MQTT topic permission bypass. the CVE-2026-44838 fix made expandtopicpermission/2 escape regex metacharacters in expanded topic-permission variables (escaperegex(V)), but escaperegexchar/1 escapes \ ^ $ . | ? + ( ) [ ] { } and omits -. When a topic permission template places {clientid} inside a [...] character class A low-privileged authenticated MQTT user controlling its clientid can broaden topic authorization (read and write) when templates embed {clientid} in a [...] This issue is fixed in versions 4.3.3 and 4.2.9 and 4.1.14 and 4.0.23.
| Product | Versions | Fixed in |
|---|---|---|
| broadcom/rabbitmq_server | ≥ 4.0.0, < 4.0.23 | 4.0.23 |
| broadcom/rabbitmq_server | ≥ 4.1.0, < 4.1.14 | 4.1.14 |
| broadcom/rabbitmq_server | ≥ 4.2.0, < 4.2.9 | 4.2.9 |
| broadcom/rabbitmq_server | ≥ 4.3.0, < 4.3.3 | 4.3.3 |