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Emerson has mitigation recommendations to remedy stack-based buffer overflow and heap-based buffer overflow vulnerabilities in its Ovation OCR400 Controller, according to a report with NCCIC.

Successful exploitation of these remotely exploitable vulnerabilities may allow privilege escalation or remote code execution, or it may halt the controller. VDLab, a collaboration of Venustech and Dongfang Electric Corporation (DEC), discovered the vulnerabilities.

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One point to note, the referenced hardware is running a software version the vendor retired in July 2015. The identified vulnerabilities exist in a third-party embedded software version discontinued by that vendor.

In addition, the vulnerable services are disabled by default in all product releases since 2007.

Cyber Security

A process control device, Emerson Ovation OCR400 Controller running Ovation Version 3.3.1 or earlier suffers from the issues.

These discontinued product versions include an embedded third-party FTP server, which is the vulnerable component. The vulnerable version of the FTP server was discontinued by that vendor several years ago.

In one issue, a stack-based buffer overflow vulnerability has been identified in the embedded third-party FTP server. The vulnerability involves improper handling of a long file name from the LIST command to the FTP service, which may cause the service to overwrite buffers, leading to remote code execution and escalation of privileges.

CVE-2019-10967 is the case number assigned to this vulnerability, which has a CVSS v3 base score of 6.3.

In addition, there is a heap-based buffer overflow vulnerability in the embedded third-party FTP server. The vulnerability involves improper handling of a long command to the FTP service, which may cause memory corruption that halts the controller or leads to remote code execution and escalation of privileges.

CVE-2019-10965 is the case number assigned to this vulnerability, which has a CVSS v3 base score of 6.8.

The product sees use mainly in the electrical (power generation) and water and wastewater sectors. It also sees action on a global basis.

No known public exploits specifically target these vulnerabilities. However, an attacker with low skill level could leverage the vulnerabilities.

Emerson is issuing a notice to its customer base with mitigation recommendations, encouraging users with this older software to upgrade to a more current version supported by Emerson and the third-party vendor.

For users with installations of the affected versions, Emerson recommends following the instructions outlined in Step 1 and Step 2 below to determine whether communication services (including FTP) have been enabled. If communication services have been enabled, Emerson recommends users return FTP services to their default (disabled) state as soon as is practical. If users are unable to make controller changes or disable communication services per the instructions below, they should restrict FTP communications to the required database and controller drops only.

How to Review Ovation Software and Hardware
Step 1 – Check the Ovation Controller Type

In Ovation Developer Studio, right-click on each controller object, select “Open” and review the “Controller Type” listed. Alternately, run a System Registration report and verify the “Model” for each controller.
• OCR400: The controller is potentially affected; continue with Step 2 (below)
• OCR161: The controller is not affected by the vulnerabilities detailed in this advisory, and can be disregarded

Step 2 – Check the Ovation Software Version

Ovation v3.0.4 and older

FTP services cannot be disabled using the Communications Services configuration detailed below. Emerson recommends users of retired systems, including Ovation v3.3.1 and older, consider upgrading to a more current version in which these issues do not exist.

However, separate mitigation involving network configuration may still be possible. Please refer to the “Review Ovation Highway Switch Configuration” section (below).

Ovation v3.1.0 – v3.3.1

Follow the “Determine Current State of Communications Services” (below).

Ovation v3.5.0 and Newer

FTP communications services cannot be enabled. This advisory does not apply to those versions.

Determine Current State of Communication Services
Two methods exist for checking the current state of controller communication services:
1. Ovation Developer Studio
2. Controller Diagnostics application

Method 1 – Use Ovation Developer Studio to determine the state and modify as needed
The steps necessary to review and/or modify communications services settings can be found in Section 5.10.1 of the Developer Studio User Guide for Ovation 3.3.1 (PWS_005981), which is available on the Ovation Users’ Group website. (this website requires registration).

Method 2 – Use Controller Diagnostics to determine the state and modify as needed
1. Open the Controller Diagnostic application on an Ovation HMI.
2. Select a drop pair by double-clicking on it in the lower-left tree.
3. In the upper-left menu, verify the “Comm Services” section is set to “Disabled” for the primary and secondary controllers.
4. If “Enabled,” left-click on the object to activate the drop-down menu and select “Disabled.”

Review Ovation Highway Switch Configurations
Systems using Cisco 2960 and/or 3750 switches on the Ovation Highway may be able to limit FTP communications (as well as telnet, rlogin, and SSH) using access control lists (ACLs). Please refer to the whitepaper “Enabling TELNET, SSH, RLOGIN & FTP Blocking on Ovation Switches,” (Support and Security | Security | Network Whitepapers).

Ovation Contact Information
Ovation users with questions or concerns regarding the impact of these vulnerabilities on Ovation should contact the Ovation-CERT via email or by phone at 1-800-445-9723, Option 3.

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