CVE-2024-36856 identifies a vulnerability in RMQTT Broker version 0.4.0, a message broker commonly used in IoT and lightweight messaging environments. The vulnerability allows remote attackers to cause a denial of service (DoS) by sending a large volume of malicious packets to the broker, which leads to a daemon crash. The root cause is related to improper handling of incoming network packets, categorized under CWE-404 (Improper Resource Shutdown or Release), which results in resource exhaustion or instability causing the broker process to terminate unexpectedly. The CVSS 3.1 base score is 7.5, reflecting a network attack vector (AV:N), low attack complexity (AC:L), no privileges required (PR:N), no user interaction (UI:N), unchanged scope (S:U), no impact on confidentiality or integrity (C:N/I:N), but high impact on availability (A:H). There are no patches currently available, and no known exploits have been reported in the wild. The vulnerability affects all deployments running RMQTT Broker 0.4.0 or potentially earlier versions if unpatched. Given the broker’s role in managing message traffic in IoT and industrial control systems, a successful attack could disrupt critical communications and services.

For European organizations, especially those involved in IoT deployments, industrial automation, and critical infrastructure, this vulnerability poses a significant risk to service availability. Disruption of RMQTT Broker services can halt message delivery, impacting operational continuity and potentially causing cascading failures in connected systems. Industries such as manufacturing, energy, transportation, and smart city implementations that rely on MQTT-based messaging could experience operational downtime. The lack of confidentiality or integrity impact limits data breach concerns, but availability loss can lead to financial losses, safety risks, and reputational damage. The ease of exploitation without authentication means attackers can launch DoS attacks remotely, increasing the threat surface. Organizations with exposed RMQTT Broker instances on public or poorly segmented networks are particularly vulnerable.

Since no official patches are currently available, European organizations should implement immediate compensating controls. These include deploying network-level protections such as rate limiting and traffic filtering to restrict the volume of packets reaching RMQTT Broker instances. Intrusion detection and prevention systems (IDS/IPS) should be configured to detect anomalous traffic patterns indicative of DoS attempts. Network segmentation should isolate MQTT brokers from untrusted networks, limiting exposure. Monitoring broker logs and system metrics for signs of instability or crashes can provide early warning. Where possible, organizations should consider upgrading to newer, patched versions once available or evaluate alternative MQTT brokers with better security postures. Additionally, applying strict access controls and disabling unnecessary services reduces the attack surface. Incident response plans should include procedures for rapid recovery from broker crashes to minimize downtime.