CVE-2017-2893 in Mongoose
Summary
by MITRE
An exploitable NULL pointer dereference vulnerability exists in the MQTT packet parsing functionality of Cesanta Mongoose 6.8. An MQTT SUBSCRIBE packet can cause a NULL pointer dereference leading to server crash and denial of service. An attacker needs to send a specially crafted MQTT packet over the network to trigger this vulnerability.
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Analysis
by VulDB Data Team • 01/06/2023
The CVE-2017-2893 vulnerability represents a critical NULL pointer dereference flaw within the Cesanta Mongoose 6.8 web server and IoT framework implementation. This vulnerability specifically targets the MQTT packet parsing functionality, which is commonly used in Internet of Things applications and embedded systems for lightweight messaging protocols. The issue arises from insufficient input validation and error handling within the MQTT SUBSCRIBE packet processing routine, creating a scenario where a malformed packet can cause the application to attempt to dereference a null pointer reference. This type of vulnerability falls under CWE-476, which categorizes NULL pointer dereference conditions as a fundamental programming error that can lead to application crashes and system instability. The vulnerability is particularly concerning in IoT environments where devices may be remotely accessible and where denial of service attacks can have significant operational impacts.
The technical exploitation of this vulnerability occurs when an attacker sends a specially crafted MQTT SUBSCRIBE packet to a vulnerable server. The packet contains malformed data that causes the Mongoose framework to process a null pointer during the parsing sequence, resulting in an immediate application crash. This crash leads to a complete denial of service condition where legitimate users cannot access the MQTT services, and the server must be manually restarted to restore functionality. The vulnerability demonstrates a classic lack of proper error handling in network protocol parsers, where the code assumes certain pointers will always contain valid data without proper validation checks. The attack requires minimal prerequisites since it only needs network access to send the malicious packet, making it particularly dangerous in environments where MQTT services are exposed to untrusted networks.
From an operational perspective, this vulnerability presents significant risks for organizations deploying IoT solutions, industrial control systems, or any networked applications that utilize the Cesanta Mongoose framework. The denial of service impact can disrupt critical operations, especially in scenarios where MQTT is used for sensor data collection, device management, or real-time communication between systems. The vulnerability is particularly problematic in environments where uptime is critical, such as manufacturing processes, smart grid systems, or emergency response communications. According to ATT&CK framework methodology, this vulnerability maps to T1499.004 which covers Network Denial of Service, and T1068 which involves Exploitation for Privilege Escalation, though the latter is less applicable given the nature of the vulnerability. Organizations using affected versions of Mongoose should immediately assess their network exposure and implement appropriate network segmentation to limit access to MQTT services.
Mitigation strategies for CVE-2017-2893 should include immediate patching of the Cesanta Mongoose framework to version 6.9 or later, which contains the necessary fixes for the NULL pointer dereference issue. Network administrators should implement proper access controls and authentication mechanisms to limit who can send MQTT packets to vulnerable systems. Additional protective measures include deploying network monitoring solutions that can detect and alert on anomalous MQTT traffic patterns, implementing rate limiting to prevent abuse, and conducting regular security assessments of IoT deployments. Organizations should also consider deploying intrusion detection systems that can identify potential exploitation attempts targeting this specific vulnerability. The fix implemented in the patched versions addresses the root cause by adding proper null pointer checks and graceful error handling in the MQTT packet parsing code, ensuring that malformed packets do not cause application crashes. This vulnerability serves as a reminder of the importance of robust input validation and error handling in network protocol implementations, particularly in embedded and IoT systems where resource constraints may lead to inadequate security controls.