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.
Severity
CVSS 3.0
6.5 medium
CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
EPSS
2.5% chance of exploitation in the next 30 days; higher than 84% of CVEs (scores of 2026-10-31)