CVE-2015-6476 in EKI-122x-BE
Summary
by MITRE
Advantech EKI-122x-BE devices with firmware before 1.65, EKI-132x devices with firmware before 1.98, and EKI-136x devices with firmware before 1.27 have hardcoded SSH keys, which makes it easier for remote attackers to obtain access via an SSH session.
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Analysis
by VulDB Data Team • 05/10/2018
The vulnerability identified as CVE-2015-6476 affects Advantech EKI-122x-BE, EKI-132x, and EKI-136x industrial network devices that operate with outdated firmware versions. These devices are commonly deployed in industrial environments for network connectivity and monitoring purposes, making their security critical to overall operational integrity. The flaw stems from the inclusion of hardcoded SSH keys within the device firmware, a practice that fundamentally undermines the security model of secure remote access. This vulnerability resides in the authentication mechanism of the SSH service, which is a core component for remote device management in industrial control systems.
The technical implementation of this vulnerability involves the embedding of static cryptographic keys directly into the firmware image during the manufacturing process. These hardcoded credentials remain unchanged across all device deployments and are essentially embedded within the device's software without any provision for user modification or rotation. This design flaw aligns with CWE-259, which addresses the use of hard-coded passwords or keys, and represents a significant deviation from secure coding practices. The presence of these static credentials means that any attacker who can obtain the specific firmware version or device model can potentially access the device without needing to perform additional reconnaissance or credential cracking activities.
From an operational perspective, this vulnerability creates a severe risk for industrial environments where these devices are deployed. Remote attackers can exploit this weakness to gain unauthorized access to the network infrastructure devices, potentially leading to complete network compromise. The vulnerability enables what is classified as a privilege escalation attack pattern within the MITRE ATT&CK framework under the T1078 technique for Valid Accounts, as the attacker can leverage these hardcoded credentials to establish persistent access. The impact extends beyond simple unauthorized access, as these devices often serve as gateways to critical industrial networks, potentially allowing attackers to move laterally within the operational technology environment.
The exploitation of this vulnerability requires minimal technical skill and effort, as attackers only need to identify the specific device model and firmware version to access the hardcoded credentials. This makes the vulnerability particularly dangerous in environments where device inventory is not properly maintained or where default credentials are not changed. Organizations using these devices face significant risk of industrial espionage, operational disruption, and potential safety hazards if these devices are compromised. The vulnerability also impacts the principle of least privilege, as the hardcoded keys provide full administrative access to the device without proper authentication mechanisms.
Mitigation strategies for this vulnerability involve immediate firmware updates to versions that address the hardcoded key issue, with the specific firmware versions mentioned in the CVE (1.65 for EKI-122x-BE, 1.98 for EKI-132x, and 1.27 for EKI-136x). Organizations should also implement network segmentation to limit access to these devices, disable unnecessary services, and establish robust device management processes. Additionally, regular security assessments of industrial control systems should include verification of device firmware versions and authentication mechanisms to prevent similar vulnerabilities from being introduced through legacy device deployments. The vulnerability underscores the importance of secure device lifecycle management and proper credential handling in industrial environments, particularly those following IEC 62443 standards for industrial automation and control systems security.