CVE-2018-3778 in aedes
Summary
by MITRE
Improper authorization in aedes version <0.35.0 will publish a LWT in a channel when a client is not authorized.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 05/01/2023
The vulnerability identified as CVE-2018-3778 represents a critical authorization flaw within the aedes MQTT broker software version 0.35.0 and earlier. This issue stems from inadequate access control mechanisms that fail to properly validate client permissions before allowing message publication. The aedes broker is a lightweight implementation of the MQTT protocol designed for Node.js environments, commonly used in IoT applications and real-time messaging systems where proper authorization is paramount for security. When a client attempts to connect to the broker without proper authentication or authorization, the system incorrectly permits the publication of Last Will and Testament (LWT) messages to designated channels, creating an unauthorized communication pathway.
The technical flaw manifests in the broker's handling of client disconnections and LWT message processing. In normal operation, LWT messages are intended to be published only when a client disconnects unexpectedly, serving as a notification mechanism for other subscribers. However, due to the improper authorization check, unauthorized clients can trigger LWT message publication even when they lack the necessary permissions to access the target channel. This vulnerability operates at the protocol level where the broker fails to verify whether a client has appropriate access rights before executing LWT publishing operations. The flaw specifically affects the authorization middleware within the aedes implementation, where the system does not properly enforce access control policies during the disconnection event handling process. This represents a direct violation of the principle of least privilege and can be categorized under CWE-284 Access Control Flaws.
The operational impact of this vulnerability extends beyond simple unauthorized message publishing, as it creates potential attack vectors for malicious actors seeking to disrupt services or gain unauthorized access to sensitive information. An attacker could exploit this weakness to publish false status updates or notifications to channels they should not have access to, potentially causing confusion in monitoring systems or enabling further attacks through information leakage. The vulnerability becomes particularly dangerous in IoT environments where MQTT brokers are used for critical infrastructure monitoring, as unauthorized LWT messages could mislead operators about system status or trigger false alarms. Additionally, this flaw could be leveraged in combination with other vulnerabilities to establish persistent unauthorized communication channels, as the attacker could use the LWT mechanism to maintain covert communication paths within the network.
Mitigation strategies for CVE-2018-3778 require immediate action to upgrade the aedes broker to version 0.35.0 or later, where the authorization checks have been properly implemented. Organizations should also implement additional network-level controls such as firewall rules to restrict access to MQTT broker endpoints and employ network segmentation to limit the exposure of MQTT services. The implementation of proper access control lists and authentication mechanisms should be enforced at multiple layers including application-level authorization, network-level access controls, and proper client certificate management. Security teams should conduct thorough audits of their MQTT broker configurations to ensure that all access controls are properly enforced and that unauthorized clients cannot trigger LWT message publication. This vulnerability aligns with ATT&CK technique T1078 Valid Accounts, as it exploits the broker's authorization system to gain unauthorized access to message channels, and T1566 Phishing, when attackers might use unauthorized LWT messages to manipulate system behavior through social engineering or deception tactics. Organizations should also implement monitoring solutions that can detect anomalous LWT message patterns and establish proper incident response procedures to address potential exploitation of this vulnerability.