CVE-2021-34431: Eclipse Mosquitto

Medium severity, CVSS 6.5. EPSS: 1.1% chance of exploitation in the next 30 days.

In Eclipse Mosquitto version 1.6 to 2.0.10, if an authenticated client that had connected with MQTT v5 sent a crafted CONNECT message to the broker a memory leak would occur, which could be used to provide a DoS attack against the broker.

Affected products

• Eclipse Mosquitto: from 1.6, up to and including 2.0.10

Published 2021-07-22. Last modified 2026-06-17.