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-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2016.2230 Moxa Active OPC Server Unquoted Service Path Escalation Vulnerability 22 September 2016 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: Moxa Active OPC Server Publisher: ICS-CERT Operating System: Windows Impact/Access: Execute Arbitrary Code/Commands -- Existing Account Increased Privileges -- Existing Account Resolution: Patch/Upgrade CVE Names: CVE-2016-5793 Original Bulletin: http://ics-cert.us-cert.gov/advisories/ICSA-16-264-01 - --------------------------BEGIN INCLUDED TEXT-------------------- Advisory (ICSA-16-264-01) Moxa Active OPC Server Unquoted Service Path Escalation Vulnerability Original release date: September 20, 2016 Legal Notice All information products included in http://ics-cert.us-cert.gov are provided "as is" for informational purposes only. The Department of Homeland Security (DHS) does not provide any warranties of any kind regarding any information contained within. DHS does not endorse any commercial product or service, referenced in this product or otherwise. Further dissemination of this product is governed by the Traffic Light Protocol (TLP) marking in the header. For more information about TLP, see http://www.us-cert.gov/tlp/. OVERVIEW Independent researcher Zhou Yu has identified an unquoted service path escalation vulnerability in Moxas Active OPC Server application. Moxa has produced a new version to mitigate this vulnerability. Zhou Yu has tested the new version to validate that it resolves the vulnerability. AFFECTED PRODUCTS Moxa reports that the vulnerability affects the following product: Active OPC Server versions older than Version 2.4.19 IMPACT Successful exploitation of this vulnerability could potentially allow an authorized but nonprivileged local user to execute arbitrary code with elevated privileges on the system. Impact to individual organizations depends on many factors that are unique to each organization. NCCIC/ICS-CERT recommends that organizations evaluate the impact of this vulnerability based on their operational environment, architecture, and product implementation. BACKGROUND Moxa is a Taiwan-based company that maintains offices in several countries around the world, including the US, UK, India, Germany, France, China, Russia, and Brazil. The affected product, Active OPC Server, is a software package that operates as an OPC driver for an HMI or SCADA system. According to Moxa, Active OPC Server is deployed across several sectors including Commercial Facilities, Critical Manufacturing, Energy, Transportation Systems, and others. Moxa estimates that this product is used primarily in the United States and Europe with a small percentage in Asia. VULNERABILITY CHARACTERIZATION VULNERABILITY OVERVIEW UNQUOTED SERVICE PATH [a] This vulnerability allows an authorized individual with access to a file system to possibly escalate privileges by inserting arbitrary code into the unquoted service path. CVE-2016-5793 [b] has been assigned to this vulnerability. A CVSS v3 base score of 8.8 has been calculated; the CVSS vector string is (AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H). [c] VULNERABILITY DETAILS EXPLOITABILITY This vulnerability is not exploitable remotely and cannot be exploited without local authorized user credentials. EXISTENCE OF EXPLOIT No known public exploits specifically target this vulnerability. DIFFICULTY An attacker with a low skill would be able to exploit this vulnerability. MITIGATION Moxa recommends replacing existing Active OPC Server installations with the new software MX-AOPC UA server. Active OPC Server is nearing end of life by the end of 2016, and no further updates will be issued. For existing Active OPC installations, Moxa suggests upgrading to Active OPC Server Version 2.4.19. If more information about patching is needed, Moxa recommends contacting the Moxa Technical Support team or by visiting the Moxa technical support web page at: http://www.moxa.com/support (link is external). ICS-CERT recommends that users take defensive measures to minimize the risk of exploitation of this vulnerability. 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 at: http://ics-cert.us-cert.gov/content/recommended-practices. 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 ICSCERT 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 (http://ics-cert.us-cert.gov/). 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-428: Unquoted Search Path or Element, http://cwe.mitre.org/data/definitions/428.html, web site last accessed September 20, 2016. b. NVD, http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2016-5793, 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:L/AC:L/PR:L/UI:N/S..., web site last accessed September 20, 2016. Contact Information For any questions related to this report, please contact ICS-CERT at: Email: ics-cert@hq.dhs.gov (link sends e-mail) Toll Free: 1-877-776-7585 International Callers: (208) 526-0900 For industrial control systems security information and incident reporting: http://ics-cert.us-cert.gov ICS-CERT continuously strives to improve its products and services. You can help by choosing one of the links below to provide feedback about this product. - --------------------------END INCLUDED TEXT-------------------- You have received this e-mail bulletin as a result of your organisation's registration with AusCERT. The mailing list you are subscribed to is maintained within your organisation, so if you do not wish to continue receiving these bulletins you should contact your local IT manager. If you do not know who that is, please send an email to auscert@auscert.org.au and we will forward your request to the appropriate person. NOTE: Third Party Rights This security bulletin is provided as a service to AusCERT's members. As AusCERT did not write the document quoted above, AusCERT has had no control over its content. The decision to follow or act on information or advice contained in this security bulletin is the responsibility of each user or organisation, and should be considered in accordance with your organisation's site policies and procedures. AusCERT takes no responsibility for consequences which may arise from following or acting on information or advice contained in this security bulletin. NOTE: This is only the original release of the security bulletin. It may not be updated when updates to the original are made. If downloading at a later date, it is recommended that the bulletin is retrieved directly from the author's website to ensure that the information is still current. Contact information for the authors of the original document is included in the Security Bulletin above. If you have any questions or need further information, please contact them directly. Previous advisories and external security bulletins can be retrieved from: http://www.auscert.org.au/render.html?cid=1980 =========================================================================== Australian Computer Emergency Response Team The University of Queensland Brisbane Qld 4072 Internet Email: auscert@auscert.org.au Facsimile: (07) 3365 7031 Telephone: (07) 3365 4417 (International: +61 7 3365 4417) AusCERT personnel answer during Queensland business hours which are GMT+10:00 (AEST). On call after hours for member emergencies only. =========================================================================== -----BEGIN PGP SIGNATURE----- Comment: http://www.auscert.org.au/render.html?it=1967 iQIVAwUBV+M+PIx+lLeg9Ub1AQgSpg/9HCpKeyAVCNXinPR7qNKrhSED0wr/xGo6 h2lg/wUTBtsxNP5/3TClD5FvZxH8DZCV3rE2yBfDar9imCxN4tCRoWPzUW0wm+Ei 5LcboS+ZmOJaIfoUyZdO/EKaruWNiM3ogXr07NNppLVtZm6MXe2eT2mVTQwIghKL LeRNt5ta3f6BgyKnmJZF72JuCF3I0j1PHhONg3i63g4bmwVYsPlwN9iS4b32TyuY kIygDcoHBN+wT9Q2eMV8DV+Ip9UprVwZRKIZzU/q3ghA4fBeMiW3AHOpPaf7zAkY 2gIsEyZdyUDJlqtOykxWj2ELc9wRe5Y/Uzc7cfoJpzJQmg7Dg+XyewpTiMEwrtYB LN89Nj+ImVg/c+yV7dAN6Deg5b5RVHWaAA8P9gyRlnPm0wXu8xU4trEco9xP4xdD p04ooSpKndD0iGEjcUHrMHnl4C4C0vbBYCh8wdrPxZFWxdhdYtN+EvAPGmwvicGn R8unW/m7FADsD9YGxN7VkxsYOUNPugZTRWYDOg/u1YFD8xIgymJ1857Dj5WvFi+k 14+3kIm40jKOGxzVEZaBLs2yhyjAP12HM4c+aHc4dZT+t9E0kCyMZ/PtX/nOuzsW xVF3NqqCMy1J92gNzkUvLcLoknGurLSIyg44dvBCD98yix3pZeHJfxMI4qxLPWtm MoJIKCWaVeA= =T47V -----END PGP SIGNATURE-----