CVE-2026-67407: RabbitMQ: Incomplete fix for CVE-2026-44838: `escape_regex_char/1` does not escape `-`, leaving room for an MQTT topic permission bypass

Severity: high (CVSS 7.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-09-25 · updated 2026-10-16
Weakness: CWE-862

Description

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.

Affected products

rabbitmq-server: from 4.0.0 before 4.0.23; from 4.1.0 before 4.1.14; from 4.2.0 before 4.2.9; from 4.3.0 before 4.3.3 — fixed in 4.0.23, 4.1.14, 4.2.9, 4.3.3

How to fix

Upgrade to a fixed version: rabbitmq-server 4.0.23, 4.1.14, 4.2.9, 4.3.3. Check the vendor advisory for mitigations.

References

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