Beckhoff Embedded PC Images and TwinCAT Components Vulnerabilities
ICSA： ICS Advisory (ICSA-16-278-02)
Gregor Bonney from FH Aachen University of Applied Sciences has identified vulnerabilities in Beckhoff’s Embedded PC Images and TwinCAT Components. He published them and reported them to Beckhoff afterward. In 2014, Beckhoff produced a new build and security advisories with instructions to mitigate these vulnerabilities.
These vulnerabilities could be exploited remotely.
Beckhoff reports that the vulnerabilities may affect the following products:
- All Beckhoff Embedded PC Images with a creation date prior to October 22, 2014, and
- All TwinCAT Components featuring Automation Device Specification (ADS) communication.
If used without proper protection, an attacker may misuse those services to gain unauthorized access to systems or read and manipulate transmitted information, especially passwords. Attackers may use ADS protocol to rapidly probe a large number of user or password combinations.
Impact to individual organizations depends on many factors that are unique to each organization. NCCIC/ICS-CERT recommends that organizations evaluate the impact of these vulnerabilities based on their operational environment, architecture, and product implementation.
Beckhoff is a German-based company.
Beckhoff Embedded PCs are hardware PC products meant to be installed in control cabinets and be configured to function in many different ways in an industrial control system. Beckhoff TwinCAT is a software product that can allow a PC to function as a real-time controller. According to Beckhoff, these products are deployed across several sectors including Critical Manufacturing, Energy, and Water and Wastewater Systems, and others. Beckhoff estimates that these products are used worldwide.
IMPROPER RESTRICTION OF EXCESSIVE AUTHENTICATION ATTEMPTSa
Attackers may use ADS protocol to rapidly probe a large number of user or password combinations.
CVE-2014-5414b has been assigned to this vulnerability. A CVSS v3 base score of 9.1 has been calculated; the CVSS vector string is (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N).c
EXPOSED DANGEROUS METHOD OR FUNCTIONd
In versions older than October 22, 2014, Beckhoff Images for Embedded PCs are delivered with the Windows CE Remote Configuration Tool reachable, enabled CE Remote Display service, and enabled telnet service. Use of these services is recommended only in trusted networks. If used without proper protection, an attacker may misuse those services to gain unauthorized access to systems or read and manipulate transmitted information, especially passwords. Precondition of the exploitation of those services is that the attacker has access to the services at the corresponding network ports (TCP 80/987/23). This implies that the services are running.
CVE-2014-5415e has been assigned to this vulnerability. A CVSS v3 base score of 9.1 has been calculated; the CVSS vector string is (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N).f
These vulnerabilities could be exploited remotely.
EXISTENCE OF EXPLOIT
No known public exploits specifically target these vulnerabilities.
An attacker with a low skill would be able to exploit these vulnerabilities.
Beckhoff recommends in their IPC Security Manual (https://download.beckhoff.com/download/Document/ipc/industrial-pc/ipc_security_en.pdf) to use network and software firewalls to block all network ports except the ones that are needed. Beckhoff also recommends that default passwords be changed during commissioning before connecting systems to the network.
In their advisories (Advisory 2014-001,g Advisory 2014-002,h Advisory 2014-003,i which were published November 17, 2014) for these issues, Beckhoff also recommends the following mitigation solutions:
- Update images to build October 22, 2014, or newer, which solve these problems by disabling the services by default.
- Disable the Windows CE Remote Configuration Tool by deleting the subtree “/remoteadmin.” The configuration of the web server paths can be found in the Windows registry at the path “HKEY_LOCAL_MACHINE\COMM\HTTPD\VROOTS\.”
- Disable startup of CE Remote Display service (cerdisp.exe) with deleting the registry key containing the “CeRDisp.exe” [-HKEY_LOCAL_MACHINE\init\Launch90].
- Disable telnet by setting the registry key [HKEY_LOCAL_MACHINE\Services\TELNETD\Flags] to dword: 4
- Restrict ADS communication to trusted networks only.
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.
- a. CWE-307: Improper Restriction of Excessive Authentication Attempts, https://cwe.mitre.org/data/definitions/307.html, web site last accessed October 04, 2016.
- b. NVD, https://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2014-5414, NIST uses this advisory to create the CVE web site report. This web site will be active sometime after publication of this advisory.
- c. CVSS Calculator, https://www.first.org/cvss/calculator/3.0#CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N, web site last accessed October 04, 2016.
- d. CWE-749: Exposed Dangerous Method or Function, https://cwe.mitre.org/data/definitions/749.html, web site last accessed October 04, 2016.
- e. NVD, https://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2014-5415, NIST uses this advisory to create the CVE web site report. This web site will be active sometime after publication of this advisory.
- f. CVSS Calculator, https://www.first.org/cvss/calculator/3.0#CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N, web site last accessed October 04, 2016.
- g. Advisory 2014-001: Potential misuse of several administrative services, https://download.beckhoff.com/download/document/product-security/Advisories/advisory-2014-001.pdf, web site last accessed October 04, 2016.
- h. Advisory 2014-002: ADS communication port allows password bruteforce, https://download.beckhoff.com/download/document/product-security/Advisories/advisory-2014-002.pdf, web site last accessed October 04, 2016.
- i. Advisory2014-003: Recommendation to change default passwords, https://download.beckhoff.com/download/document/product-security/Advisories/advisory-2014-003.pdf, web site last accessed October 04, 2016.