CVE-2023-37781 in EMQX
Summary
by MITRE • 07/17/2023
An issue in the emqx_sn plugin of EMQX v4.3.8 allows attackers to execute a directory traversal via uploading a crafted .txt file.
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Analysis
by VulDB Data Team • 01/18/2026
The vulnerability identified as CVE-2023-37781 resides within the emqx_sn plugin of EMQX version 4.3.8, representing a critical directory traversal flaw that enables remote attackers to manipulate file system operations through malicious file uploads. This issue specifically manifests when the system processes crafted .txt files during the upload process, allowing unauthorized access to arbitrary files on the server filesystem. The vulnerability stems from inadequate input validation and sanitization mechanisms within the plugin's file handling routines, creating an attack surface where malicious actors can exploit the lack of proper path validation to navigate beyond intended directories.
The technical exploitation of this vulnerability follows a directory traversal pattern that aligns with CWE-22, which categorizes improper limitation of a pathname to a restricted directory. Attackers can craft specially formatted .txt files containing directory traversal sequences such as ../ or ..\ that bypass normal file upload restrictions. When the emqx_sn plugin processes these files, the insufficient validation allows the system to interpret these sequences and access files outside the designated upload directories. This flaw operates at the application layer and can be exploited remotely without requiring authentication, making it particularly dangerous in production environments where EMQX brokers handle sensitive data exchanges.
The operational impact of this vulnerability extends beyond simple file access, as it can enable attackers to read system configuration files, access sensitive logs, retrieve database credentials, or even execute arbitrary code if the system allows file execution. The affected EMQX v4.3.8 version represents a significant security risk for organizations relying on MQTT broker functionality, particularly those in industrial IoT environments where message brokers handle critical communications. The vulnerability can be leveraged to gain unauthorized access to message queues, potentially compromising the integrity and confidentiality of communications between IoT devices, sensors, and backend systems. From an ATT&CK framework perspective, this vulnerability maps to T1078 Valid Accounts and T1566 Phishing, as it enables attackers to escalate privileges and maintain persistence within the network infrastructure.
Organizations should implement immediate mitigations including upgrading to EMQX versions that have addressed this vulnerability, implementing strict file upload validation mechanisms, and configuring proper access controls to limit file system access. The recommended remediation strategy involves applying the vendor-provided patches, disabling unnecessary file upload functionality, and implementing web application firewalls to detect and block malicious traversal attempts. Additionally, network segmentation and monitoring should be enhanced to detect unusual file access patterns and potential exploitation attempts. Security teams should also conduct thorough audits of all EMQX plugin configurations and ensure that file upload directories are properly restricted to prevent privilege escalation attacks. The vulnerability demonstrates the importance of input validation in middleware applications and highlights the need for comprehensive security testing of all file handling components in distributed messaging systems.