CVE-2020-27213: High severity ethernut nut/os vulnerability

Published Oct 10, 2023

Updated

An issue was discovered in Ethernut Nut/OS 5.1. The code that generates Initial Sequence Numbers (ISNs) for TCP connections derives the ISN from an insufficiently random source. As a result, an attacker may be able to determine the ISN of current and future TCP connections and either hijack existing ones or spoof future ones. While the ISN generator seems to adhere to RFC 793 (where a global 32-bit counter is incremented roughly every 4 microseconds), proper ISN generation should aim to follow at least the specifications outlined in RFC 6528.

Affected Software

14 affected components

Ethernut Nut\/os=5.1

Multiple Nut/Net, Version 5.1 and prior

Multiple CycloneTCP, Version 1.9.6 and prior

Multiple NDKTCPIP, Version 2.25 and prior

Multiple FNET, Version 4.6.3

Multiple uIP-Contiki-OS (end-of-life [EOL]), Version 3.0 and prior

Multiple uC/TCP-IP (EOL), Version 3.6.0 and prior

Multiple uIP-Contiki-NG, Version 4.5 and prior

Multiple uIP (EOL), Version 1.0 and prior

Multiple picoTCP-NG, Version 1.7.0 and prior

Multiple picoTCP (EOL), Version 1.7.0 and prior

Multiple MPLAB Net, Version 3.6.1 and prior

Multiple Nucleus NET, All versions prior to Version 5.2

Multiple Nucleus ReadyStart for ARM, MIPS, and PPC, All versions prior to Version 2012.12

Event History

Oct 10, 2023

CVE Published

via MITRE·12:00 AM

Data Sourced

via MITRE·12:00 AM

Description

Data Sourced

05:15 PM

Description

Parent advisories

This vulnerability appears in the following advisories.

ICSA-21-042-01

Frequently Asked Questions

What is the severity of CVE-2020-27213?

CVE-2020-27213 is considered a critical vulnerability due to its potential to allow TCP connection hijacking.

What products are affected by CVE-2020-27213?

CVE-2020-27213 impacts multiple products including Ethernut Nut/OS 5.1, CycloneTCP 1.9.6 and prior, and various other TCP/IP stacks.

How do I fix CVE-2020-27213?

To mitigate CVE-2020-27213, it is recommended to update to the latest secure version of the affected software.

What is the cause of CVE-2020-27213?

CVE-2020-27213 is caused by the use of an insufficiently random source for generating Initial Sequence Numbers in TCP connections.

Can CVE-2020-27213 allow unauthorized access?

Yes, CVE-2020-27213 may allow an attacker to hijack existing TCP connections, leading to unauthorized access.