CVE-2017-16934 in DBLTek
Summary
by MITRE
The web server on DBL DBLTek devices allows remote attackers to execute arbitrary OS commands by obtaining the admin password via a frame.html?content=/dev/mtdblock/5 request, and then using this password for the HTTP Basic Authentication needed for a change_password.csp request, which supports a "<%%25call system.exec:" string in the passwd parameter.
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Analysis
by VulDB Data Team • 01/05/2025
The vulnerability identified as CVE-2017-16934 affects DBL DBLTek network devices and represents a critical security flaw in the web server implementation that enables remote command execution. This vulnerability stems from inadequate authentication and input validation mechanisms within the device's web interface, creating a pathway for attackers to escalate privileges and gain full system control. The flaw specifically exploits the device's handling of password change requests through the change_password.csp endpoint, which fails to properly sanitize user input before processing system commands. The vulnerability is particularly concerning because it requires minimal prerequisites for exploitation, making it highly accessible to threat actors with basic network reconnaissance capabilities.
The technical exploitation pathway begins with an attacker accessing the frame.html endpoint with a specific parameter pointing to /dev/mtdblock/5, which contains the device's configuration data including administrative credentials. This approach leverages the device's lack of proper access controls for reading sensitive system files, allowing unauthorized users to extract administrative passwords without proper authentication. Once the administrative credentials are obtained, attackers can proceed to the change_password.csp endpoint where the actual command execution vulnerability resides. The passwd parameter in this endpoint accepts specially crafted input that includes the "<%%25call system.exec:" string, which serves as a directive for the web server to execute arbitrary operating system commands with the privileges of the web server process. This mechanism directly maps to CWE-78, which describes improper neutralization of special elements used in OS commands, and represents a classic command injection vulnerability that bypasses traditional input validation.
The operational impact of this vulnerability extends far beyond simple privilege escalation, as it provides attackers with complete control over the affected devices. Once exploited, attackers can execute any command available on the system, potentially leading to data exfiltration, network reconnaissance, or use of the compromised device as a pivot point for attacking other systems within the network. The vulnerability affects the integrity and confidentiality of the device's operational environment, as attackers can modify system configurations, install malicious software, or establish persistent backdoors. The implications are particularly severe in industrial control systems or network infrastructure environments where DBLTek devices may be deployed, as these systems often handle critical operations that require high availability and security assurances. Organizations using these devices face potential compliance violations under standards such as NIST 800-53 and ISO 27001 due to the exposure of unauthorized administrative access.
Mitigation strategies for CVE-2017-16934 must address both the immediate exploitation vectors and the underlying architectural weaknesses that enabled the vulnerability. The most effective immediate solution involves applying vendor-provided firmware updates that correct the authentication bypass mechanism and implement proper input sanitization for command execution parameters. Network segmentation should be implemented to isolate affected devices from critical network segments, reducing the potential blast radius of successful exploitation attempts. Access controls should be strengthened through the implementation of multi-factor authentication, network access control lists, and regular credential rotation policies. Security monitoring should be enhanced to detect anomalous access patterns and command execution attempts through the change_password.csp endpoint. From an ATT&CK framework perspective, this vulnerability maps to techniques such as T1078 for valid accounts and T1059 for command and scripting interpreter, while the initial access through the frame.html endpoint represents a privilege escalation technique. Organizations should also consider implementing network intrusion detection systems that can identify and block the specific request patterns associated with this exploit, and conduct regular security assessments to identify similar vulnerabilities in other network infrastructure components.