Improper Encoding or Escaping of Output in RabbitMQ Server - CVE-2026-67407
Published: July 24, 2026 / Updated: September 28, 2026
Vulnerability identifier: #VU139293
CSH Severity: Low
CVSS v4: 7.1 [CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-67407
CWE-ID: CWE-116
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote user to bypass MQTT topic authorization.
The vulnerability exists due to improper escaping of special elements in rabbit_auth_backend_internal.erl escape_regex_char/1 and topic permission expansion when processing MQTT topic permission templates that place {client_id} inside a character class. A remote user can supply a crafted client_id value to bypass MQTT topic authorization.
The issue affects read and write topic checks only when templates embed {client_id} within a [...] character class.
Affected software
RabbitMQ Server
How to mitigate CVE-2026-67407
Install security update from vendor's website.
RabbitMQ Server - addressed in versions 4.0.23, 4.1.14, 4.2.9, 4.3.3