FlashMQ vulnerabilities

FlashMQ before version 1.26.2 allows authorized clients to exceed the permitted over-commit of their write buffer, triggering an internal safe-guard exception. This exception is in a path that cannot be caught, causing a server abort.

In FlashMQ prior to version 1.26.1, a remote client with retained publish permission can crash the broker when both set_retained_message_defer_timeout and set_retained_message_defer_timeout_spread are configured to non-default values, resulting in denial of service. If anonymous retained publishing is allowed, no authentication is required; otherwise, the attacker needs the corresponding publish permission. The issue is patched in version 1.26.1.

FlashMQ is a MQTT broker/server, designed for multi-CPU environments. Prior to version 1.23.2, any authenticated user can create sessions and have them collect QoS messages. When not sent to a client, these are then not released upon (eventual) session expiration. Version 1.23.2 fixes the issue.