CVE-2023-0809 in Mosquitto
Summary
by MITRE • 10/25/2023
In Mosquitto before 2.0.16, excessive memory is allocated based on malicious initial packets that are not CONNECT packets.
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Analysis
by VulDB Data Team • 10/25/2023
The vulnerability identified as CVE-2023-0809 affects the Mosquitto MQTT broker software version 2.0.15 and earlier, representing a significant memory allocation flaw that can be exploited through crafted malicious packets. This issue stems from the broker's handling of initial network communications where it fails to properly validate packet types before allocating memory resources. The vulnerability specifically targets the memory management logic that processes incoming packets during the connection establishment phase, creating a potential avenue for resource exhaustion attacks. Attackers can exploit this weakness by sending specially crafted packets that trigger excessive memory allocation without proper bounds checking, leading to system instability and potential denial of service conditions.
The technical flaw manifests in the broker's protocol parsing implementation where it does not adequately differentiate between valid CONNECT packets and other packet types during the initial handshake process. When processing these malicious packets, the software allocates memory buffers based on malformed or unexpected packet structures without proper input validation. This memory allocation behavior follows a pattern where the system reserves resources based on packet headers or size indicators that have been manipulated by attackers to appear legitimate while containing malicious payload characteristics. The vulnerability is classified under CWE-772, which deals with missing release of memory after effective lifetime, and represents a classic example of resource exhaustion through improper memory management. The flaw essentially allows an attacker to consume system resources at a rate that exceeds normal operational parameters, creating conditions that can lead to system crashes or degraded performance.
From an operational impact perspective, this vulnerability poses serious risks to MQTT broker deployments that handle untrusted network traffic or lack proper network segmentation controls. The memory allocation behavior can be exploited to consume system resources rapidly, potentially leading to complete system crashes or denial of service conditions that affect legitimate users. Organizations relying on Mosquitto for critical IoT communications, industrial control systems, or enterprise messaging infrastructure face significant operational risks when this vulnerability remains unpatched. The attack vector is particularly concerning because it can be executed with minimal privileges and does not require authentication, making it a low-effort but high-impact threat. This vulnerability aligns with ATT&CK technique T1499.001, which covers network disruption attacks through resource exhaustion, and can be leveraged as part of broader attack chains targeting IoT and industrial control systems. The memory exhaustion can also impact system availability and potentially provide a foundation for more sophisticated attacks that exploit the resulting system instability.
Mitigation strategies for CVE-2023-0809 should prioritize immediate patching of affected Mosquitto installations to version 2.0.16 or later where the memory allocation logic has been corrected. Organizations should implement network-level controls such as firewall rules to restrict access to MQTT broker ports and employ rate limiting mechanisms to prevent excessive packet processing. Additional defensive measures include monitoring memory usage patterns and implementing intrusion detection systems that can identify unusual memory allocation behaviors. Network segmentation should be enforced to limit exposure of MQTT brokers to untrusted networks, and proper input validation should be implemented at all network boundaries. The vulnerability highlights the importance of proper memory management practices in network services and underscores the need for regular security assessments of critical infrastructure components. System administrators should also consider implementing automated monitoring solutions that can detect anomalous memory consumption patterns and trigger alerts when resource usage exceeds normal operational thresholds, providing early warning capabilities against potential exploitation attempts.