CVE-2018-12551: Eclipse Mosquitto

High severity, CVSS 8.1. EPSS: 1.5% chance of exploitation in the next 30 days.

When Eclipse Mosquitto version 1.0 to 1.5.5 (inclusive) is configured to use a password file for authentication, any malformed data in the password file will be treated as valid. This typically means that the malformed data becomes a username and no password. If this occurs, clients can circumvent authentication and get access to the broker by using the malformed username. In particular, a blank line will be treated as a valid empty username. Other security measures are unaffected. Users who have only used the mosquitto_passwd utility to create and modify their password files are unaffected by this vulnerability.

Affected products

• Eclipse Mosquitto: from 1.0, up to and including 1.5.5

Published 2019-03-27. Last modified 2026-06-17.