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Multiple TCP/IP stack flaws could leave millions of devices open to attack

The stacks are susceptible to Mitnick attacks

An abstract mock up of a blue padlock on a binary code background

Security researchers have discovered vulnerabilities in multiple TCP/IP stacks that affect millions of internet-connected devices and could enable hackers to hijack them.

Researchers at Forescout, a cyber security firm, have uncovered nine exploits, dubbed “Number:jack,“ in multiple TCP/IP stacks that improperly generate Initial Sequence Numbers (ISNs) within TCP connections. This meant the flaws left devices’ TCP connections open to attacks. ISNs ensure that every TCP connection between two devices is unique and that there are no collisions so that third parties cannot interfere with an ongoing connection.

The stacks are susceptible to the so-called “Mitnick attack,” named after legendary computer hacker Kevin Mitnick. 

In total, 11 stacks were analyzed: uIP, FNET, picoTCP, Nut/Net, lwIP, cycloneTCP, uC/TCP-IP, MPLAB Net, TI-NDKTCPIP, Nanostack, and Nucleus NET. Millions of devices, including everything from IT file servers to IoT embedded components, use uIP, FNET, picoTCP and Nut/Net. Researchers found improperly generated ISNs in nine of the 11 stacks analyzed.

Researchers said they disclosed the vulnerabilities to the affected vendors and maintainers in October 2020. 

“Most vendors have already issued patches and/or mitigation recommendations to users. The developers of Nut/Net are working on a solution, and Forescout has not received a response from the uIP developers,” the report added.

Researchers have released an open-source script that uses active fingerprinting to detect devices running the affected stacks to help deal with the problem. They also urged organizations to monitor progressive patches released by affected device vendors and devise a remediation plan for their vulnerable asset inventory.

For vulnerable IoT and OT devices, researchers said to use segmentation to minimize network exposure and the likelihood of compromise without impacting mission-critical functions or business operations. “Segmentation and zoning can also limit the blast radius and business impact if a device is compromised,” they added.

David Kennefick, product architect at Edgescan, told ITPro there needs to be a hard think about the technology being implemented in the IoT world. 

“Secure design needs to be implemented from the device inception phase, the technology should be created with a support period in mind with an EOL (end of life) plan, if this doesn’t happen, we will keep finding the same issues in the same stacks for the next 20 years. The broad usage of these devices means a security concern can quickly turn into a safety concern,” he said.

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