Cybersecurity Advisory: CISCO Smart Install (SMI) Vulnerability

C3 Threat Advisory Reference# 04162018-1 

CISCO Smart Install (SMI) Vulnerability

Cisco has acknowledged the misuse of the Smart Install protocol on its network access layer switches running the IOS and IOS XE software leading to reports of the affected devices being reloaded causing network downtimes. Cisco subsequently released advisories addressing vulnerabilities in this feature, which if exploited, give the ability to a remote attacker to trigger the reload of the affected device, causing a Denial of Service (DoS). The attacker may also be able to execute arbitrary code on the device. 


Cisco Smart Install is a feature that offers zero-touch deployment for new devices using “plug-and-play” configuration and image management. Using this feature, a customer can ship the Cisco device to any location, install and power it on without any additional configuration. The Smart Install feature stays enabled on the device after its deployment and since it does not use any authentication mechanisms by design, it leaves the device susceptible to this attack. 

The vulnerability currently affects devices which have the “Client” role within the Smart Install configuration. Devices with the “Director” role are not affected as confirmed by Cisco. This advisory is rated Critical and the vulnerabilities are identified with the following IDs: CVE-2018-0171 and CVE-2018-0156. 

Exploit Details

The vulnerability is exploited due to improper validation of packet data which can be accepted by a vulnerable device since this feature does not require any authentication. When an attacker sends a crafted Smart Install message to a device listening on port TCP 4786, which if successful, could lead to a buffer overflow on the device that may eventually cause an indefinite loop resulting in a watchdog crash or a reload of the device. 

The Smart Install Exploitation Tool (SIET) is readily available on the internet making the exploit of this vulnerability more accessible to script kiddies or threat actors. A recent scan on the internet revealed more than 4000 vulnerable devices in Canada that may be susceptible to this attack. 


A successful exploitation of this vulnerability may have the following impact: 

  • Change the TFTP server address on the device to a TFTP destination server that may be controlled by the attacker. 
  • Copy the device’s startup-config to the said TFTP server. 
  • Replace the existing startup-config with the attacker’s version of the startup-config file. 
  • Upgrade the IOS image on the device with the one propagated by the attacker. 
  • Execute high-privileged configuration mode CLI commands on the device. 
  • Reboot and reload the device, which may reset the device to the factory default configuration. 
  • Execute arbitrary code on the device. 
  • Cause an indefinite loop on the device triggering a watchdog crash. 
  • Disrupt regular operations and business services. 
  • Financial losses due to unavailability of network resources. 
  • Potential harm to an organization’s reputation. 


Cisco has released the Cisco IOS Software Checker on its official page so that network administrators and users can enter their Cisco device software IOS release version to check if they are affected by this vulnerability. Alternately, the following commands on a Cisco device can ascertain the status of the Smart Install feature: 

  • Switch1# show vstack config 
  • Check the role of the device; if it’s “Client”, then the device may be susceptible. 
  • Switch1# show version 
  • Copy the firmware version of the Cisco IOS or IOS XE software and paste it on the Cisco IOS Software Checker to confirm if the device is vulnerable or not. 

Mitigation or Remediation Actions by Organizations 

There are no workarounds to address this vulnerability. The following options are available to network administrators: 

Customers who do not use the Smart Install feature: 

  • Disable the feature using the “no vstack” configuration command on the device. 

Customers who use the Smart Install feature only for zero-touch deployment: 

  • Once the zero-touch installation is complete, disable the Smart Install feature using the “no vstack” configuration command on the device. 
  • Propagate this command on all devices deployed using this feature. 
  • Add this command to the IOS configuration which is pushed on each Smart Install Client as part of the zero-touch deployment. 
  • If the “no vstack” command is not supported by the IOS, apply access lists (ACLs) on client switches to block traffic on port TCP 4786. 

Customers who use Smart Install feature for management beyond the zero-touch deployment: 

  • Apply access lists (ACLs) to allow only the Smart Install “Director” to send traffic to the Smart Install “Client” switches on port TCP 4786. 
  • Block any other traffic on this port from all IPs on the client switches. 
  • Apply these access lists on all interfaces. 

Customers can also block traffic on port TCP 4786 on the network firewalls. 

Customers can detect the use of SMI on Cisco devices using the following command: 

  • alert tcp any any -> any 4786 (msg:”Smart Install Protocol”; flow:established,only_stream; content:”|00 00 00 01 00 00 00 01|”; offset:0; depth:8; fast_pattern;) 

Customers can also detect the use of SIET on Cisco devices using the following command: 

  • alert tcp any any -> any 4786 (msg: “SmartInstallExploitationTool_GetConfig”; flow: established; content:”|00 00 00 01 00 00 00 01 00 00 00 08 00 00 04 08|”; offset:0; depth:16; fast_pattern; content:”copy|20|”;) 
  • alert tcp any any -> any 4786 (msg:”SmartInstallExploitationTool_ChangeConfig”; flow:established; content:”|00 00 00 01 00 00 00 01 00 00 00 03 00 00 01 28|”; offset:0; depth:16; fast_pattern; content:”://”;) 

Actions by Difenda

  • The Cyber Command Team at Difenda has put together specialized use cases to detect the use of SIET or SMI for the clients forwarding relevant logs to us. 
  • Additionally, periodic reports are being executed to check the traffic details on port TCP 4786. 
  • For the clients for whom Difenda offers firewall device management services, the said port has been added to the block list for traffic originating from the internet and the firewall threat signatures have been updated. 


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Biography coming soon.

Megan Miller

Megan Miller’s energy and passion for learning flow into all aspects of her work. As the Growth Manager, North America, she brings a background in sciences which she has transitioned to the tech sector in her role at Difenda.

With a Bachelors of Science in Geology, Megan is a lifelong learner who is voracious about learning anything she can get her hands on about cybersecurity. Her positive energy has built a sales strategy with a focus on expanding in the United States while nurturing the Canadian presence. She is responsible for recruiting and training the sales team. Together with the company’s leadership, she creates the sales process and the company’s product strategy in order to better serve the customer base. This ensures that our customers have a highly trained and highly motivated team to help them every step of the way, Megan has completed Microsoft SC-900 training and working towards mastering Microsoft.

Whether at work or play, Megan is fully committed. She took her love of hockey all the way to the semi-professional level as a competitive hockey player. Megan loves all things sports including water skiing, scuba diving, cycling, and snowboarding. She also enjoys time with family and reading about alternative energy, innovation, and cybersecurity.

Natasha Phanor

As the Microsoft Partner Manager at Difenda, Natasha Phanor is responsible for driving growth within our Microsoft Partnership. With six years in the industry, she offers a fresh, energetic approach, and the ability to focus on our customer’s needs throughout the entire process. Natasha has the innate ability to foresee customer needs and solve problems before they arise, which creates a smooth road for each customer she encounters.

As the recipient of the Outstanding Services Partner of the Year Award in 2018, it is clear that Natasha responds quickly to customer needs, creates a platform for understanding a customer’s business requirements, and walks them through the process to ensure their complete satisfaction.

In her spare time, Natasha is as energetic and passionate as she is on the job. A self-proclaimed foodie-extraordinaire, she enjoys dinner parties, traveling, downhill skiing, hiking, biking, and reading. Natasha has a Bachelor of Fine Arts, specializing in Dance, from Ryerson University.

Ian Miersch

Ian Miersch has energy to spare, and uses his eclectic background to make a positive mark on the cybersecurity industry. As Vice President of Finance & Human Resources, Ian Miersch is responsible for overseeing scalable business growth as Difenda expands throughout North America. But it is the way he does it that sets him apart. By leveraging his engineering background and critical thinking skills, he has been able to develop unique strategies that balance the company’s current business needs with its long-term growth plans. And the results of his unique background and drive mean that the company is growing in a fiscally responsible manner, all with the customer’s needs at the forefront.

With a Bachelor’s of Mechanical Engineering, coupled with an MBA in Finance, both from McMaster University, Ian’s ability to analyze data and make informed decisions is augmented by his ability to understand all facets of the business. He has a holistic understanding of the craft, from operations to project delivery and management, to his niche in financial planning. Ian’s ten years of experience in the industry mean that he has seen it all, and knows how to create a dynamic team and manage the resources needed for success.

Outside of work, he uses his energy to help others through the Big Brothers and Big Sisters Program, earning the Group Recreation Volunteer of the Year Status.

Ian also enjoys exploring and hiking with his three young children, exercising (so he can keep up with them), and reading professional development books. He is an avid but generally heartbroken fan of the Toronto sports teams, including the Blue Jays, Maple Leafs, and Raptors.

Derek Nugent

Derek Nugent, Vice President, Revenue lives by the motto “Be early, be better.” Derek leads our Revenue team and is responsible for the customer’s journey with Difenda. His high energy level and creativity have built high performing teams, whether at the Herjavec Group, CDW, or in his current leadership role at Difenda.

After earning a Bachelor Administration and Management degree from the Academy of Learning, Derek started in the information technology industry in 2004 and transitioned to the cybersecurity industry in 2014. With so much experience in a wide-variety of roles, he is poised to take the team at Difenda to the next level.

He excels at leading revenue strategies, new market entry, partnership engagement, and customer acquisition and retention. His work ethic and interest in rising to the top motivate his sales teams, who respond well to his passion and zeal. Under his tutelage, they are able to achieve attractive lead generation, YOY growth, and sizable deals. Derek works tirelessly to build a better team, and his constituents follow his road to success, which ultimately leads to a rewarding experience for the customer.

Even when volunteering, Derek is all in. He was a volunteer with Big Brothers Big Sisters from 2005-2015, earning Group Recreation Volunteer of the Year Status.

And when he isn’t busy leading the team to the acme of sales, he enjoys spending time with his wife and two kids, running, working out, watching thrillers, action and dramatic television shows

Manoj Arora

Manoj Arora, Difenda’s Founder and CEO has always been ahead of the curve in Technology and Cyber Security. After securing his engineering degree in Computer Science, he wrote his first mobile banking application when he was just 23 years old. This accomplishment certainly set him apart from the crowd and prepared him for a lifetime of innovation and success in his field. At just 25 years old, he was selected as the youngest Cyber Security Officer for one of the largest banks in Asia.

As a globetrotting young cyber security professional, Manoj was instrumental in designing cyber security infrastructure and controls for some of the largest institutions around the world. Depth of his expertise and passion to serve customers at the highest level of competence and integrity lead to Difenda. Founded in 2008, Difenda is a rapidly growing cybersecurity firm operating in North America and Asia.

As the CEO at Difenda, Manoj drives the strategic vision to protect our customers and enable our team members to deliver our services in line with core values- competence, integrity, and innovation. Currently one of Microsoft’s leading North American partners, Difenda reflects Manoj’ single-minded focus on our customers. Difenda is fully vested in success of its customers and takes pride in considering our success as a byproduct of our customers. Manoj has always been committed to building a great team and forging strong partnerships to serve our customers with standards that top our industry.

When he is not busy bringing cybersecurity to the world, Manoj enjoys playing golf and squash, and continues to travel the world.

Lisa Templeton

Lisa Templeton is the perfect combination of human empathy and technological prowess. In her role as People Services Manager, she takes care of our team members to support them in their daily work, as well as on their personal life paths. Happy employees make for happy customers, and Lisa excels in giving our employees the tools they need for success in order to become the best possible versions of themselves. Along with employee formation, she shines in the service delivery support domain to continuously improve the process. Her 24 years of experience in IT Operations and Service Management help her create quality and efficiency at Difenda.

Having attended the Information Systems Management certificate program at Ryerson University, and with various other certifications to her credit, Lisa is perceptive and innovative when it comes to information technology, but also sensitive to the needs of her human constituents. Responsible for achieving the first privately owned company HDI Support Center certification in Canada, she has also designed and implemented Service Management excellence programs and 24×7 IT Operations departments for multiple IT organizations, and has created corporate rewards and recognition programs to keep her employees engaged and motivated.

On the personal side, Lisa passionately supports the cause of breast cancer research, having lost her mother to the disease. She reads voraciously in her spare time, and enjoys the art of home renovation. The summer months also bring time on her boat and exploring new hiking trails.

Miranda McCurdy

Miranda McCurdy uses her myriad super powers in all aspects of her job and personal life. As the Marketing Director at Difenda, Miranda McCurdy brings over a decade of experience to the table, which includes expertise in all facets of operations, brand management, and content marketing, as well as a multitude of successful strategies for the ever-expanding digital world. She is an expert at simplifying the message the company is trying to send, filling in gaps in the information, and strengthening the content in order to create compelling narratives that strengthen the brand and developing programs that bring teams together.

With several Addy Awards issued by the American Advertising Federation Cleveland to her credit, and her never say die attitude, Miranda understands both the broader picture and the minute details that are needed to successfully market a product. With her abilities to harness both the talent needed to spread the message, as well as to create the message itself, she is an integral cog in the company’s ability to communicate with customers and other stakeholders.

When she is not building a brand, she shares her ability to fill the gaps in her community by volunteering with Habitat for Humanity, the Special Olympics, and the Charleston Food Bank. In her spare time, Miranda spends time with her family, enjoys fitness and health, paddle boarding, reading, and arts and crafts.

Juliana Zaremba

Connections are the name of the game for Juliana Zaremba. As Strategic Partnerships Director, she is responsible for Difenda’s channel partnerships and the development and ownership of the channel partner program. She is also responsible for the global Microsoft Partnership, including the creation of strategic plans with MSFT contacts that will facilitate the continued growth of the business and establish certification and training protocols in all security technologies. Her role is multifaceted, as she acquires partners, manages relationships with them, and develops strategies that will provide cutting edge security solutions to our customer base. Another integral aspect of her job is to facilitate growth.

With a Bachelor’s in Math from the University of Waterloo and 14 years of experience from her previous roles at Herjavec Group and CDW, her cutting edge focus and ability to develop long-lasting relationships and strategies provides world class security solutions to our customer base.

Juliana thrives on connections outside of work as well. She is a philanthropist and contributor with Women4Change based in Hamilton. This group of local women is passionate about supporting local causes, and she focuses her efforts around Women in STEM. She is also a member of Club Italia in Niagara Falls and supports their youth events throughout the year.

When not managing the Microsoft Global partnership, Juliana enjoys reading, often reading several books at once. Juliana enjoys exploring the Niagara Escarpment with her family, as well as sharing meals and experiences with her extended family. Juliana’s competitive nature has her always trying new things, like Whoop band challenges and Peloton.

Jeffry Jacob

Biography Coming Soon