In Mosquitto before 1.4.12, pattern based ACLs can be bypassed by clients that set their username/client id to '#' or '+'. This allows locally or remotely connected clients to access MQTT topics that they do have the rights to. The same issue may be present in third party authentication/access control plugins for Mosquitto.

References

• https://nvd.nist.gov/vuln/detail/CVE-2017-7650
• https://bugs.eclipse.org/bugs/show_bug.cgi?id=516765
• http://mosquitto.org/2017/05/security-advisory-cve-2017-7650/
• http://www.debian.org/security/2017/dsa-3865
• http://www.securityfocus.com/bid/98741