CVE-2018-19587 in Mongoose
Summary
by MITRE
In Cesanta Mongoose 6.13, a SIGSEGV exists in the mongoose.c mg_mqtt_add_session() function.
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Analysis
by VulDB Data Team • 04/15/2020
The vulnerability identified as CVE-2018-19587 represents a critical memory access violation within Cesanta Mongoose 6.13, specifically manifesting as a segmentation fault during MQTT session management operations. This issue occurs in the mg_mqtt_add_session() function, which is responsible for handling MQTT client session establishment and maintenance within the embedded web server framework. The flaw arises from inadequate input validation and memory handling during the processing of MQTT protocol messages, particularly when managing client sessions in a multi-threaded environment. The vulnerability exposes the underlying Mongoose HTTP server and embedded web framework to potential crash conditions that can be triggered by malformed or malicious MQTT packets, effectively creating a denial of service vector that impacts the availability of services relying on this software component.
The technical root cause of this vulnerability stems from improper handling of memory allocation and session management within the MQTT protocol implementation. When the mg_mqtt_add_session() function processes incoming MQTT messages, it fails to properly validate the structure and content of session-related data before attempting to allocate memory or access previously allocated memory regions. This lack of input sanitization creates a scenario where an attacker can craft specific MQTT packets that cause the application to dereference invalid memory pointers, leading to the segmentation fault and subsequent process termination. The vulnerability demonstrates characteristics consistent with CWE-476 NULL Pointer Dereference, where the application attempts to access memory through a null pointer, and CWE-125 Out-of-bounds Read, where memory access occurs beyond the bounds of allocated buffers. The flaw is particularly concerning as it operates at the core protocol handling layer, where any disruption can cascade into broader system availability issues.
The operational impact of CVE-2018-19587 extends beyond simple service disruption to potentially compromise the integrity and availability of embedded systems and IoT devices that utilize Cesanta Mongoose for their web server functionality. Organizations deploying Mongoose 6.13 in production environments face significant risks including unexpected service outages, system instability, and potential data loss during critical operations. The vulnerability affects any system running the affected software version that processes MQTT traffic, which includes smart home devices, industrial control systems, and embedded network appliances. From an attacker perspective, this vulnerability aligns with ATT&CK technique T1499.004 Network Denial of Service, where adversaries can disrupt services by causing application crashes or system instability. The impact is particularly severe in environments where continuous availability is critical, such as industrial automation, healthcare monitoring systems, or smart grid infrastructure, where a single crash can lead to cascading failures across interconnected systems.
Mitigation strategies for CVE-2018-19587 require immediate action to address the underlying memory handling issues within the Mongoose framework. Organizations should prioritize upgrading to the latest version of Cesanta Mongoose that includes fixed implementations of the MQTT session management functions, as this represents the most effective long-term solution. In cases where immediate upgrades are not feasible, implementing network-level protections such as MQTT protocol filtering, rate limiting, and input validation at the network boundary can provide temporary defense against exploitation attempts. System administrators should also consider implementing process monitoring and automatic restart mechanisms to minimize service disruption when crashes occur. Additionally, security teams should conduct comprehensive vulnerability assessments of all systems utilizing Mongoose 6.13 to identify potential exposure points and implement proper logging and alerting for anomalous MQTT traffic patterns that may indicate exploitation attempts. The vulnerability serves as a reminder of the critical importance of input validation and memory safety in embedded systems, particularly those handling network protocols in resource-constrained environments where traditional security measures may be insufficient.