CVE-2021-31881: Siemens Apogee Modular Building Controller Firmware

High severity, CVSS 7.5. EPSS: 1.5% chance of exploitation in the next 30 days.

A vulnerability has been identified in Capital Embedded AR Classic 431-422 (All versions), Capital Embedded AR Classic R20-11 (All versions < V2303). When processing a DHCP OFFER message, the DHCP client application does not validate the length of the Vendor option(s), leading to Denial-of-Service conditions. (FSMD-2021-0008)

Affected products

• Siemens Apogee Modular Building Controller Firmware: any version
• Siemens Apogee Modular Equiment Controller Firmware: any version
• Siemens Apogee Pxc Compact Firmware: any version
• Siemens Apogee Pxc Modular Firmware: any version
• Siemens Capital Vstar: any version
• Siemens Nucleus Net: any version
• Siemens Nucleus Readystart v3: before 2012.08 (fixed in 2012.08)
• Siemens Nucleus Source Code: any version
• Siemens Talon Tc Compact Firmware: any version
• Siemens Talon Tc Modular Firmware: any version

Published 2021-11-09. Last modified 2026-06-17.