A series of 13 vulnerabilities identified in the Nucleus TCP/IP stack could be exploited to execute code remotely, cause a denial of service condition, or to obtain sensitive information, enterprise device security firm Forescout warns.
Collectively referred to as NUCLEUS:13, the issues likely affect safety-critical devices, such as anesthesia machines, patient monitors and other types of devices used in healthcare. Other types of operational technology (OT) systems are also impacted.
The most important of the newly identified issues is CVE-2021-31886 (CVSS score of 9.8), a stack-based buffer overflow that exists because the FTP server fails to properly validate the length of the “USER” command. An attacker could exploit the vulnerability to cause a denial of service (DoS) condition or to achieve remote code execution.
Two other similar issues in the FTP server (related to the improper validation of the length of the “PWD/XPWD” and “MKD/XMKD” commands) were assessed with a severity rating of high.
Of the remaining bugs, nine are considered high severity and could be exploited to leak sensitive information or cause DoS conditions. The last issue in the set is a medium-severity bug in the ICMP that could be exploited to send ICMP echo reply messages to arbitrary network systems.
Some of these vulnerabilities, Forescout explains, were addressed in existing versions of the Nucleus TCP/IP stack, yet they were never issued CVE identifiers. Patches are available for all 13 security holes.
Developed by Accelerated Technology, Inc. (ATI) in 1993, Nucleus NET, the TCP/IP stack in the Nucleus real-time operating system (RTOS), is now owned by Siemens. Over its 28-year life, Nucleus has been deployed in devices across several verticals, including healthcare, automotive, and industrial systems.
The official Nucleus website claims the RTOS is deployed on over 3 billion devices, but Forescout believes that most of these are, in fact, components such as chipsets and baseband processors. The researchers say they were able to find only thousands of potentially vulnerable devices connected to the Internet and that the healthcare sector appears to be affected the most.
Siemens has also published advisories describing the impact of the vulnerabilities on its own products.
Organizations are advised to identify within their environments all devices that are running Nucleus and apply the available patches or mitigations as soon as possible, as well as to ensure proper network segmentation is enforced. They should also monitor network traffic to identify any malicious packets and disable FTP/TFTP if not needed, or use switch-based DHCP control mechanisms.