3S-Smart Software Solutions GmbH CODESYS Web Server

CVSS v3 9.8

ATTENTION: Remotely exploitable/low skill level to exploit.

Vendor: 3S-Smart Software Solutions GmbH

Equipment: CODESYS Web Server

Vulnerabilities: Arbitrary File Upload, Stack Buffer Overflow

AFFECTED PRODUCTS

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.

IMPACT

Successful exploitation of these vulnerabilities could allow arbitrary files to be uploaded to the CODESYS Web Server without authorization. Additionally, an attacker may be able to crash the application or execute arbitrary code.

MITIGATION

3S-Smart Software Solutions GmbH recommends that device manufacturers who program their devices with CODESYS refer to the device directory to determine if they may be affected. The device directory can be found at the following location:

http://devices.codesys.com/device-directory.html

3S-Smart Software Solutions GmbH recommends that users register for an account and download patch V.1.1.9.18 from the following location:

http://store.codesys.com/codesys-23.html

NCCIC/ICS-CERT recommends that users take defensive measures to minimize the risk of exploitation of these vulnerabilities. Specifically, users should:

• Minimize network exposure for all control system devices and/or systems, and ensure that they are not accessible from the Internet.
• Locate control system networks and remote devices behind firewalls, and isolate them from the business network.
• When remote access is required, use secure methods, such as Virtual Private Networks (VPNs), recognizing that VPNs may have vulnerabilities and should be updated to the most current version available. Also recognize that VPN is only as secure as the connected devices.

ICS-CERT reminds organizations to perform proper impact analysis and risk assessment prior to deploying defensive measures.

ICS-CERT also provides a section for control systems security recommended practices on the ICS-CERT web page. Several recommended practices are available for reading and download, including Improving Industrial Control Systems Cybersecurity with Defense-in-Depth Strategies.

Additional mitigation guidance and recommended practices are publicly available in the ICS‑CERT Technical Information Paper, ICS-TIP-12-146-01B--Targeted Cyber Intrusion Detection and Mitigation Strategies, that is available for download from the ICS-CERT web site.

Organizations observing any suspected malicious activity should follow their established internal procedures and report their findings to ICS-CERT for tracking and correlation against other incidents.

No known public exploits specifically target these vulnerabilities.

VULNERABILITY OVERVIEW

A specially crafted web server request may allow the upload of arbitrary files to the CODESYS Web Server without authorization which may allow remote code execution.

CVE-2017-6027 has been assigned to this vulnerability. A CVSS v3 base score of 9.8 has been assigned; the CVSS vector string is (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H).

A malicious user could overflow the stack buffer by providing overly long strings to functions that handle the XML. Because the function does not verify string size before copying to memory, the attacker may then be able to crash the application or run arbitrary code.

CVE-2017-6025 has been assigned to this vulnerability. A CVSS v3 base score of 9.8 has been assigned; the CVSS vector string is (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H).

RESEARCHER

David Atch of CyberX discovered the vulnerabilities and has tested the patch.

BACKGROUND

Critical Infrastructure Sector(s): Critical Manufacturing, Energy

Countries/Areas Deployed: Worldwide

Company Headquarters Location: Kempten, Germany

• 3S-Smart Software Solutions