CVE-2015-3939 in IDS RTU 850C
Summary
by MITRE
Directory traversal vulnerability in the NC854 and NC856 modules for IDS RTU 850C devices allows remote authenticated users to read arbitrary files via unspecified vectors involving an internal web server, as demonstrated by reading a TELNET credentials file.
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Analysis
by VulDB Data Team • 04/02/2019
The vulnerability identified as CVE-2015-3939 represents a critical directory traversal flaw affecting IDS RTU 850C devices with NC854 and NC856 modules. This vulnerability exists within the internal web server implementation of these industrial control devices, creating a significant security risk for operational technology environments. The flaw enables remote authenticated attackers to exploit unspecified vectors that allow arbitrary file reading capabilities, fundamentally compromising the device's security posture and potentially exposing sensitive operational data.
The technical nature of this vulnerability stems from inadequate input validation within the internal web server component of the IDS RTU 850C devices. When authenticated users interact with the web interface, the system fails to properly sanitize file path inputs, allowing malicious requests to traverse directory structures and access files outside the intended scope. This directory traversal mechanism operates at the application layer and specifically targets the internal web server that serves management interfaces for these industrial devices. The vulnerability is particularly concerning because it requires only authentication credentials to exploit, meaning that attackers who have gained access to legitimate user accounts can leverage this flaw to escalate their privileges and access sensitive configuration files.
The operational impact of this vulnerability extends beyond simple file reading capabilities, as demonstrated by the specific case of accessing TELNET credentials files. This exposure of authentication credentials creates a cascading security risk where attackers can potentially compromise multiple systems within the industrial network. The vulnerability affects devices in critical infrastructure environments where the IDS RTU 850C serves as a security monitoring and control device, making the potential damage significant for industrial control systems. Organizations using these devices face the risk of unauthorized access to network credentials, configuration files, and potentially sensitive operational data that could be used for further attacks or system compromise.
This vulnerability aligns with CWE-22, which describes improper limitation of a pathname to a restricted directory, commonly known as path traversal or directory traversal attacks. The flaw also maps to ATT&CK technique T1078 which covers valid accounts and T1566 which covers credential access through various methods including exploitation of software vulnerabilities. The attack vector demonstrates how authenticated access can be leveraged to bypass security controls, representing a common pattern in industrial control system attacks where initial access is gained through legitimate means and then used to escalate privileges and access sensitive information. Organizations should implement comprehensive network segmentation, regular security assessments, and timely patch management to address this vulnerability and prevent unauthorized access to critical industrial control systems. The exposure of TELNET credentials specifically highlights the importance of secure credential management and the need for robust authentication mechanisms in industrial environments where legacy protocols may still be in use.