VU#815128: Embedded TCP/IP stacks have memory corruption vulnerabilities

Overview

Multiple open-source embedded TCP/IP stacks, commonly used in Internet of Things (IoT) and embedded devices, have several vulnerabilities stemming from improper memory management. These vulnerabilities are also tracked as ICS-VU-633937 and JVNVU#96491057 as well as the name AMNESIA:33.

Description

Embedded TCP/IP stacks provide essential network communication capability using TCP/IP networking to many lightweight operating systems adopted by IoT and other embedded devices. These software stacks can also be used in the latest technologies such as Edge Computing. The following embedded TCP/IP stacks were discovered to have 33 memory related vulnerabilities included in this advisory:

• uIP: https://github.com/adamdunkels/uip
• Contiki-OS and Contiki-NG: https://www.contiki-ng.org/
• PicoTCP and PicoTCP-NG: http://picotcp.altran.be
• FNET: http://fnet.sourceforge.net/
• Nut/OS: http://www.ethernut.de/en/software/

These networking software stacks can be integrated in various ways, including compiled from source, modified and integrated, and linked as a dynamic or static libraries, allowing for a wide variety of implementations. As an example, projects such as Apache Nuttx and open-iscsi have adopted common libraries and software modules, thus inheriting some of these vulnerabilities with varying levels of impact. The diversity of implementations and the lack of supply chain visibility has made it difficult to accurately assess the impact, usage as well as the potential exploitability of these vulnerabilities.

In general, most of these vulnerabilities are caused by memory management bugs, commonly seen in lightweight software implementations in Real Time Operating Systems (RTOS) and IoT devices. For specific details on these vulnerabilities, see the Forescout advisory that provides technical details. Due to the lack of visibility of these software usage, Forescout has released an open source version of Detector that can be used to identify potentially vulnerable software.

Impact

The impact of these vulnerabilities vary widely due to the combination of build and runtime options customized while including these in embedded devices. In summary, a remote, unauthenticated attacker may be able to use specially-crafted network packets to cause the vulnerable device to behave in unexpected ways such as a failure (denial of service), disclosure of private information, or execution of arbitrary code.

Solution

Apply updates

Update to the latest stable version of the affected embedded TCP/IP software that address these recently disclosed vulnerabilities. If you have adopted this software from an upstream provider, contact the provider to get appropriate updates that need to be integrated into your software. Concerned end-users of IoT and embedded devices that implement these vulnerable TCP/IP software stacks should contact their vendor or the closest reseller to obtain appropriate updates.

Follow best-practices

We recommend that you follow best practices when connecting IoT or embedded devices to a network:

• Avoid exposure of IoT and embedded devices directly over the Internet and use a segmented network zone when available.
• Enable security features such as deep-packet inspection and firewall anomaly detection when available to protect embedded and IoT devices.
• Ensure secure defaults are adopted and disable unused features and services on your embedded devices.
• Regularly update firmware to the vendor provided latest stable version to ensure your device is up to date.

Acknowledgements

Jos Wetzels, Stanislav Dashevskyi, Amine Amri and Daniel dos Santos of Forescout Technologies researched and reported these vulnerabilities.

This document was written by Vijay Sarvepalli.

Vendor Information

References

• https://www.forescout.com/amnesia33
• https://us-cert.cisa.gov/ics/advisories/ICSA-20-343-01
• https://www.iotsecurityfoundation.org/securing-the-embedded-iot-world/
• https://krebsonsecurity.com/2018/01/some-basic-rules-for-securing-your-iot-stuff/
• https://skelia.com/articles/iot-security-why-your-toaster-needs-a-firewall/