Critical ICSA-21-313-03 13 CVEs

Siemens Nucleus RTOS TCP/IP Stack

Published Nov 9, 2021 · Updated May 6, 2025 · Revision 3

Vendor: Siemens Product: Nucleus NET Product: Nucleus ReadyStart V3 Product: Nucleus ReadyStart V4 Product: Nucleus Source Code

Summary

The TCP/IP stack and related services (FTP, TFTP) of the networking component (Nucleus NET) in Nucleus Real-Time Operating System (RTOS) contain several vulnerabilities, also known as "NUCLEUS:13" and as documented below.

Siemens has released updates for several affected products and recommends to update to the latest versions. Siemens recommends countermeasures for products where updates are not available.

Vulnerabilities 13

High 8.2

CVE-2021-31346

A vulnerability has been identified in Capital Embedded AR Classic 431-422 (All versions), Capital Embedded AR Classic …

Siemens Capital Embedded AR Classic R20-11 Capital Embedded AR Classic 431-422 SIMOTICS CONNECT 400 ICS / OT

Nov 9, 2021
High 7.5

CVE-2021-31345

A vulnerability has been identified in Capital Embedded AR Classic 431-422 (All versions), Capital Embedded AR Classic …

Siemens Capital Embedded AR Classic R20-11 Capital Embedded AR Classic 431-422 PLUSCONTROL 1st Gen ICS / OT

Nov 9, 2021
High 7.5

CVE-2021-31889

A vulnerability has been identified in Capital Embedded AR Classic 431-422 (All versions), Capital Embedded AR Classic …

Siemens Capital Embedded AR Classic 431-422 Capital Embedded AR Classic R20-11 SIMOTICS CONNECT 400 ICS / OT

Nov 9, 2021
High 7.5

CVE-2021-31890

A vulnerability has been identified in Capital Embedded AR Classic 431-422 (All versions), Capital Embedded AR Classic …

Siemens Capital Embedded AR Classic R20-11 Capital Embedded AR Classic 431-422 SIMOTICS CONNECT 400 ICS / OT

Nov 9, 2021
High 7.1

CVE-2021-31881

A vulnerability has been identified in Capital Embedded AR Classic 431-422 (All versions), Capital Embedded AR Classic …

Siemens Capital Embedded AR Classic 431-422 Capital Embedded AR Classic R20-11 ICS / OT

Nov 9, 2021
High 7.1

CVE-2021-31883

A vulnerability has been identified in Capital Embedded AR Classic 431-422 (All versions), Capital Embedded AR Classic …

Siemens Capital Embedded AR Classic 431-422 Capital Embedded AR Classic R20-11 ICS / OT

Nov 9, 2021
Medium 6.5

CVE-2021-31882

A vulnerability has been identified in Capital Embedded AR Classic 431-422 (All versions), Capital Embedded AR Classic …

Siemens Capital Embedded AR Classic 431-422 Capital Embedded AR Classic R20-11 ICS / OT

Nov 9, 2021
Medium 5.3

CVE-2021-31344

A vulnerability has been identified in Capital Embedded AR Classic 431-422 (All versions), Capital Embedded AR Classic …

Siemens Capital Embedded AR Classic R20-11 Capital Embedded AR Classic 431-422 SIMOTICS CONNECT 400 ICS / OT

Nov 9, 2021
Unscored —

CVE-2021-31884

A vulnerability has been identified in APOGEE MBC (PPC) (BACnet) (All versions), APOGEE MBC (PPC) (P2 Ethernet) (All ve…

Siemens APOGEE PXC Compact (P2 Ethernet) APOGEE PXC Modular (P2 Ethernet) TALON TC Modular (BACnet) ICS / OT

Nov 9, 2021
Unscored —

CVE-2021-31885

A vulnerability has been identified in APOGEE MBC (PPC) (BACnet) (All versions), APOGEE MBC (PPC) (P2 Ethernet) (All ve…

Siemens TALON TC Compact (BACnet) APOGEE PXC Compact (P2 Ethernet) APOGEE PXC Modular (P2 Ethernet) ICS / OT

Nov 9, 2021
Unscored —

CVE-2021-31886

A vulnerability has been identified in APOGEE MBC (PPC) (BACnet) (All versions), APOGEE MBC (PPC) (P2 Ethernet) (All ve…

Siemens APOGEE PXC Compact (BACnet) APOGEE PXC Modular (BACnet) TALON TC Compact (BACnet) ICS / OT

Nov 9, 2021
Unscored —

CVE-2021-31887

A vulnerability has been identified in APOGEE MBC (PPC) (BACnet) (All versions), APOGEE MBC (PPC) (P2 Ethernet) (All ve…

Siemens APOGEE PXC Compact (BACnet) APOGEE PXC Modular (BACnet) TALON TC Compact (BACnet) ICS / OT

Nov 9, 2021
Unscored —

CVE-2021-31888

A vulnerability has been identified in APOGEE MBC (PPC) (BACnet) (All versions), APOGEE MBC (PPC) (P2 Ethernet) (All ve…

Siemens TALON TC Modular (BACnet) APOGEE PXC Compact (BACnet) APOGEE PXC Modular (BACnet) ICS / OT

Nov 9, 2021

Revision history

2025-05-06 #3
Revision - Fixing typos
2021-12-14 #2
Moved product CAPITAL VSTAR to a separate advisory (SSA-620288)
2021-11-09 #1
Publication Date

References

SSA-044112: Multiple Vulnerabilities (NUCLEUS:13) in the TCP/IP Stack of Nucleus RTOS - TXT Version
https://cert-portal.siemens.com/productcert/txt/ssa-044112.txt
SSA-044112: Multiple Vulnerabilities (NUCLEUS:13) in the TCP/IP Stack of Nucleus RTOS - PDF Version
https://cert-portal.siemens.com/productcert/pdf/ssa-044112.pdf
ICS Advisory ICSA-21-313-03 - Web Version
https://www.cisa.gov/news-events/ics-advisories/icsa-21-313-03
Recommended Practices
https://www.cisa.gov/uscert/ics/alerts/ICS-ALERT-10-301-01
Recommended Practices
https://www.cisa.gov/resources-tools/resources/ics-recommended-practices
Recommended Practices
https://www.cisa.gov/topics/industrial-control-systems
Recommended Practices
https://us-cert.cisa.gov/sites/default/files/recommended_practices/NCCIC_ICS-CERT_Defense_in_Depth_2016_S508C.pdf
Recommended Practices
https://www.cisa.gov/sites/default/files/publications/Cybersecurity_Best_Practices_for_Industrial_Control_Systems.pdf
Recommended Practices
https://www.cisa.gov/uscert/ics/tips/ICS-TIP-12-146-01B