ICS Advisory

Software Toolbox Top Server Resource Exhaustion Vulnerability

Last Revised
Alert Code


Adam Crain of Automatak and Chris Sistrunk of Mandiant have identified a resource exhaustion vulnerability in the Software Toolbox Top Server application. Software Toolbox has produced a new version that mitigates this vulnerability.

This vulnerability could be exploited remotely.


The following Software Toolbox Top Server versions are affected:

  • Software Toolbox Top Server Versions 5.16 and earlier.


An attacker who exploits this response processing vulnerability may be able to crash the OPC Server application software running on the target.

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.


Software Toolbox is a US-based company that maintains offices primarily in Matthews, North Carolina. The TOP Server application is used as an industrial third-party connectivity communication software for OPC and embedded device communication users, system integrators, and in OEM automated processes worldwide.

The affected product, Top Server, is a Microsoft Windows-based software that facilitates connectivity to multiple DNP3 compliant devices such as HMI, RTU, PLC, sensors and meters.

According to Software Toolbox, Top Server is deployed worldwide across several sectors including Chemical, Commercial Facilities, Critical Manufacturing, Energy, Food and Agriculture, Information Technology, and Water and Wastewater Systems.



UNCONTROLLED RESOURCE CONSUMPTION (RESOURCE EXHAUSTION)CWE-400: Uncontrolled Resource Consumption ('Resource Exhaustion'), http://cwe.mitre.org/data/definitions/400.html, web site last accessed February 24, 2015.

A vague interpretation of the DNP3 protocol may allow a specially crafted response to create large numbers of entries in the master in some implementations. This is not a universal problem for all DNP3 users, vendors, or integrators, but it may occur.

CVE-2014-5425NVD, http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2014-5425, web site last accessed February 24, 2015. has been assigned to this vulnerability. A CVSS v2 base score of 7.5 has been assigned; the CVSS vector string is (AV:N/AC:L/Au:N/C:P/I:P/A:P).CVSS Calculator, http://nvd.nist.gov/cvss.cfm?version=2&vector=AV:N/AC:L/Au:N/C:P/I:P/A:P, web site last accessed February 24, 2015.



This vulnerability could be exploited remotely.


No known public exploits specifically target this vulnerability.


An attacker with a moderate skill would be able to exploit this vulnerability.


Remote devices should not return a variation of 0 to a master, and a master that encounters a zero length message from a remote should stop processing that message.

DNP3 Application Note AN2013-004b Validation of Incoming DNP3 Data, published August 13, 2014, addresses this issue. This bulletin may be downloaded at:


Software Toolbox has produced a new version of Top Server software, V5.17.495.0, which resolves the vulnerability. Information about the new version is available at the Software Toolbox support site:


Telephone support is available to trial and registered users 8 a.m. to 5 p.m. US Eastern Time (GMT‑5), Monday through Friday.

US Toll Free – 1-888-665-3678

Global – 1-704-849-2773

ICS-CERT encourages asset owners to take additional defensive measures to protect against this and other cybersecurity risks.

  • 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 VPN is only as secure as the connected devices.

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

Additional mitigation guidance and recommended practices are publicly available in the ICS‑CERT Technical Information Paper, ICS-TIP-12-146-01B—Targeted Cyber Intrusion 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.

This product is provided subject to this Notification and this Privacy & Use policy.


Software Toolbox