CVE-2018-5399 in DCU 210E
Summary
by MITRE
The Auto-Maskin DCU 210E firmware contains an undocumented Dropbear SSH server, v2015.55, configured to listen on Port 22 while the DCU is running. The Dropbear server is configured with a hard-coded user name and password combination of root / amroot. The server is configured to use password only authentication not cryptographic keys, however the firmware image contains an RSA host-key for the server. An attacker can exploit this vulnerability to gain root access to the Angstrom Linux operating system and modify any binaries or configuration files in the firmware. Affected releases are Auto-Maskin DCU-210E RP-210E: Versions prior to 3.7 on ARMv7.
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Analysis
by VulDB Data Team • 02/01/2025
The Auto-Maskin DCU 210E device presents a critical security vulnerability through an embedded Dropbear SSH server that operates without proper authorization mechanisms. This vulnerability stems from an undocumented component within the firmware that listens on the standard SSH port 22, creating an unauthorized entry point for malicious actors. The device operates on an Angstrom Linux distribution and contains a version of Dropbear SSH server from 2015, specifically v2015.55, which represents a known vulnerable implementation that has been identified in various security assessments and threat intelligence reports. The vulnerability is particularly concerning as it provides persistent access to the underlying operating system through default credentials that are well-documented in security research communities. The hard-coded authentication credentials of root/amroot create an easily exploitable weakness that bypasses normal authentication procedures and provides immediate administrative access to the system.
The technical implementation of this vulnerability involves the Dropbear SSH server being configured to accept password authentication only, which eliminates the security benefits of public key cryptography and makes the system susceptible to brute force attacks even if the default credentials are changed. The firmware image includes an RSA host key, which suggests that the server was properly configured for host authentication, but this does not compensate for the weak authentication mechanism that allows attackers to gain root access through the hardcoded credentials. This configuration aligns with CWE-798, which addresses the use of hardcoded credentials in software, and represents a fundamental flaw in the security architecture of the device. The device's ARMv7 architecture and firmware versions prior to 3.7 create a specific attack surface that has been documented in multiple security advisories and penetration testing reports.
The operational impact of this vulnerability extends far beyond simple unauthorized access, as it allows complete compromise of the device's operating system and firmware integrity. Once an attacker gains root access through the SSH server, they can modify any binaries or configuration files within the firmware, potentially leading to persistent backdoors, data exfiltration, or disruption of critical operations. The ability to modify firmware components means that attackers can effectively take control of the device's functionality and potentially use it as a pivot point for accessing other systems within the network. This vulnerability represents a significant risk to industrial control systems and can be exploited through the MITRE ATT&CK framework's T1021.004 technique for remote services and T1059.001 for command and scripting interpreter, respectively, which are commonly used by threat actors targeting industrial environments. The compromise of such devices can have cascading effects on operational technology networks and may violate compliance requirements for industrial security standards.
Organizations should immediately implement network segmentation to isolate these devices from critical systems and apply firmware updates from the vendor to address this vulnerability. The recommended mitigation includes disabling the SSH service entirely if it is not required for legitimate operations, or implementing strict network access controls to limit who can access port 22 on these devices. Security monitoring should include detection of SSH connection attempts to these devices, particularly those using the hardcoded credentials. The vulnerability demonstrates the importance of proper device lifecycle management and the need for vendors to implement secure-by-default configurations that do not include undocumented services or hardcoded credentials. Additionally, organizations should conduct comprehensive vulnerability assessments of their industrial control systems to identify similar undocumented components that may present similar security risks, as this represents a pattern of insecure implementation practices that have been observed in multiple industrial device vulnerabilities and security assessments conducted across various sectors.