CVE-2017-15376 in MobaXterm
Summary
by MITRE
The TELNET service in Mobatek MobaXterm 10.4 does not require authentication, which allows remote attackers to execute arbitrary commands via TCP port 23.
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Analysis
by VulDB Data Team • 11/24/2019
The vulnerability identified as CVE-2017-15376 represents a critical security flaw in Mobatek MobaXterm version 10.4 where the TELNET service operates without proper authentication mechanisms. This configuration creates an exploitable entry point that allows remote attackers to gain unauthorized access to systems running the affected software. The vulnerability specifically affects TCP port 23 which is the standard port for TELNET protocol communications, making it easily discoverable and accessible to potential attackers. The absence of authentication requirements means that any remote entity can establish a connection and execute arbitrary commands on the target system, effectively providing full control over the affected machine. This flaw directly violates fundamental security principles and represents a severe configuration error that undermines the integrity and confidentiality of the system.
The technical implementation of this vulnerability stems from the improper configuration of the TELNET service within MobaXterm 10.4. When the TELNET service is enabled, it should require valid user credentials to establish a connection and execute commands. However, in this specific version, the service defaults to an unauthenticated state, allowing anyone with network access to the target system to connect and perform administrative operations. This represents a classic example of insecure default configurations, which falls under CWE-255 - "Credentials Management Vulnerability" and CWE-798 - "Use of Hard-coded Credentials." The flaw operates at the network service level where the TELNET daemon fails to implement proper authentication checks before granting access to command execution capabilities. Attackers can leverage this vulnerability through simple network scanning tools to identify systems with the vulnerable service running and immediately exploit it without requiring any special privileges or complex attack vectors.
The operational impact of this vulnerability extends far beyond simple unauthorized access, as it provides attackers with complete control over the affected systems. Remote command execution capabilities enable attackers to install malware, modify system configurations, steal sensitive data, or use the compromised system as a pivot point for further attacks within the network. The implications are particularly severe in enterprise environments where MobaXterm might be used for legitimate remote administration purposes but inadvertently exposes systems to unauthorized access. This vulnerability can be exploited by attackers at scale through automated scanning tools that target TCP port 23, making it a prime target for botnets and automated attack campaigns. The attack surface is further expanded because TELNET is often used in environments where other security controls may not be robust, creating additional opportunities for lateral movement and persistent access within compromised networks.
Mitigation strategies for CVE-2017-15376 should focus on immediate service configuration changes and long-term security enhancements. The primary recommendation is to disable the TELNET service entirely within MobaXterm if it is not required for legitimate operations, as the service should not be running in unauthenticated mode. System administrators should implement proper authentication mechanisms for any remote access services and ensure that only necessary services are enabled on target systems. Network segmentation and firewall rules should be configured to block access to TCP port 23 from external networks unless absolutely required. The vulnerability aligns with ATT&CK technique T1021.004 - "Remote Services: Telnet" which emphasizes the importance of securing remote access protocols. Organizations should also implement regular security audits to identify and remediate similar configuration flaws across their infrastructure. Upgrading to newer versions of MobaXterm where the service has been properly secured or implementing network monitoring solutions that can detect unauthorized TELNET connections will help prevent exploitation of this vulnerability. Additionally, security awareness training for administrators should emphasize the dangers of running unauthenticated services and the importance of proper configuration management practices.