CVE-2017-6027 in CODESYS Web Server
Summary
by MITRE
An Arbitrary File Upload issue was discovered in 3S-Smart Software Solutions GmbH CODESYS Web Server. The following versions of CODESYS Web Server, part of the CODESYS WebVisu web browser visualization software, are affected: CODESYS Web Server Versions 2.3 and prior. A specially crafted web server request may allow the upload of arbitrary files (with a dangerous type) to the CODESYS Web Server without authorization which may allow remote code execution.
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Analysis
by VulDB Data Team • 12/25/2020
The CVE-2017-6027 vulnerability represents a critical arbitrary file upload flaw in CODESYS Web Server software developed by 3S-Smart Software Solutions GmbH. This vulnerability specifically affects CODESYS WebVisu web browser visualization software versions 2.3 and earlier, creating a significant security risk for industrial control systems and web-based visualization environments. The vulnerability stems from insufficient input validation and file type checking mechanisms within the web server implementation, allowing malicious actors to bypass authentication and authorization controls to upload potentially harmful files to the target system.
The technical exploitation of this vulnerability occurs through specially crafted web server requests that manipulate the file upload functionality of the CODESYS Web Server. When an attacker successfully uploads a malicious file, the system does not properly validate the file type or content, enabling the upload of dangerous file formats such as executable binaries, script files, or other malicious payloads. This flaw directly relates to CWE-434, which describes insecure file upload vulnerabilities where applications accept files from untrusted sources without proper validation. The vulnerability creates a pathway for remote code execution, as the uploaded files can be executed within the context of the web server process, potentially granting attackers full control over the affected system.
The operational impact of CVE-2017-6027 extends beyond simple unauthorized file uploads to encompass complete system compromise and potential industrial control system disruption. In industrial environments where CODESYS Web Server is deployed for web-based visualization of control systems, this vulnerability could enable attackers to gain persistent access to critical infrastructure, potentially leading to operational technology (OT) system compromise. The remote code execution capability allows attackers to execute arbitrary commands on the server, install backdoors, exfiltrate sensitive data, or even manipulate industrial processes. This vulnerability is particularly dangerous in environments where the web server operates with elevated privileges, as it could provide attackers with the means to escalate their privileges and move laterally within the network.
Mitigation strategies for CVE-2017-6027 should focus on immediate patching and implementation of additional security controls. Organizations should upgrade to CODESYS Web Server versions 2.4 or later, which contain fixes for this vulnerability. In the interim, network administrators should implement strict file type validation at the application level, rejecting uploads of dangerous file extensions such as .exe, .bat, .cmd, .sh, .pl, .php, and .asp. The implementation of web application firewalls and intrusion detection systems can help monitor and block suspicious upload attempts. Additionally, the principle of least privilege should be enforced by running the web server with minimal required permissions and ensuring that uploaded files are stored in separate directories with restricted access. This vulnerability aligns with ATT&CK technique T1190, which covers exploitation of remote services, and T1059, which addresses command and script injection, demonstrating how this single vulnerability can enable multiple attack vectors in a comprehensive compromise strategy.