CVE-2021-31885: Siemens Apogee Modular Building Controller Firmware

High severity, CVSS 7.5. EPSS: 1.2% chance of exploitation in the next 30 days.

A vulnerability has been identified in APOGEE MBC (PPC) (BACnet) (All versions), APOGEE MBC (PPC) (P2 Ethernet) (All versions), APOGEE MEC (PPC) (BACnet) (All versions), APOGEE MEC (PPC) (P2 Ethernet) (All versions), APOGEE PXC Compact (BACnet) (All versions < V3.5.4), APOGEE PXC Compact (P2 Ethernet) (All versions < V2.8.19), APOGEE PXC Modular (BACnet) (All versions < V3.5.4), APOGEE PXC Modular (P2 Ethernet) (All versions < V2.8.19), Desigo PXC00-E.D (All versions >= V2.3 and < V6.30.016), Desigo PXC00-U (All versions >= V2.3 and < V6.30.016), Desigo PXC001-E.D (All versions >= V2.3 and < V6.30.016), Desigo PXC100-E.D (All versions >= V2.3 and < V6.30.016), Desigo PXC12-E.D (All versions >= V2.3 and < V6.30.016), Desigo PXC128-U (All versions >= V2.3 and < V6.30.016), Desigo PXC200-E.D (All versions >= V2.3 and < V6.30.016), Desigo PXC22-E.D (All versions >= V2.3 and < V6.30.016), Desigo PXC22.1-E.D (All versions >= V2.3 and < V6.30.016), Desigo PXC36.1-E.D (All versions >= V2.3 and < V6.30.016), Desigo PXC50-E.D (All versions >= V2.3 and < V6.30.016), Desigo PXC64-U (All versions >= V2.3 and < V6.30.016), Desigo PXM20-E (All versions >= V2.3 and < V6.30.016), Nucleus NET (All versions), Nucleus ReadyStart V3 (All versions < V2017.02.4), Nucleus ReadyStart V4 (All versions < V4.1.1), Nucleus Source Code (All versions), PLUSCONTROL 1st Gen (All versions), TALON TC Compact (BACnet) (All versions < V3.5.4), TALON TC Modular (BACnet) (All versions < V3.5.4). TFTP server application allows for reading the contents of the TFTP memory buffer via sending malformed TFTP commands. (FSMD-2021-0009)

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 2017.02.4 (fixed in 2017.02.4)
• Siemens Nucleus Readystart v4: before 4.1.1 (fixed in 4.1.1)
• 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.