Security Experts:

Organizations Warned About DoS Flaws in Popular Open Source Message Brokers

Organizations have been warned about denial of service (DoS) vulnerabilities found in RabbitMQ, EMQ X and VerneMQ, three widely used open source message brokers.

Message brokers enable applications, systems and services to communicate with each other and exchange information by translating messages between formal messaging protocols. One of the protocols they use is Message Queuing Telemetry Transport (MQTT).

A researcher at the Synopsys Cybersecurity Research Center discovered that specially crafted MQTT messages can cause excessive memory consumption in RabbitMQ (owned by VMware), EMQ X and VerneMQ, leading to the operating system terminating the application.

A type of malformed message that causes a DoS condition has been identified for each of the three message brokers, but there does not appear to be a single message that impacts all three brokers.

“Message brokers can be the nerve center of a complex system,” Jonathan Knudsen, the researcher who discovered the flaws, told SecurityWeek. “If the message broker isn't working, then the various components of the system cannot communicate. Whatever services are provided by that system are unavailable until the message broker is restored.”

As for how the vulnerabilities can be exploited, Knudsen explained, “These vulnerabilities can be exploited by any system that has access to the message broker. The broker can be configured to require authentication or refuse connections from unrecognized endpoints which would limit external attacks. But for an attacker with access to one of the vulnerable message brokers, the vulnerabilities can be exploited simply by delivering a badly formed network packet, which can be done with a very simple script.”

According to EMQ, its message broker has been downloaded more than 2 million times and it has over 5,000 global enterprise users. RabbitMQ claims to have tens of thousands of users, including small startups and large enterprises. VerneMQ is used by companies such as Microsoft, Volkswagen, Siemens and Swisscom.

The vulnerabilities, rated high severity, are tracked as CVE-2021-22116 (RabbitMQ), CVE-2021-33175 (EMQ X) and CVE-2021-33176 (VerneMQ). They were patched in April, March and May, respectively.

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Eduard Kovacs (@EduardKovacs) is a contributing editor at SecurityWeek. He worked as a high school IT teacher for two years before starting a career in journalism as Softpedia’s security news reporter. Eduard holds a bachelor’s degree in industrial informatics and a master’s degree in computer techniques applied in electrical engineering.