CVE-2021-31887

Name: CVE-2021-31887
Creator: NVD / NIST
Published: 2021-11-09T12:15:09.587+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 8.8/10EPSS 2.37%

Last modified Jun 17, 2026

CVE-2021-31887 is a high-severity vulnerability rated 8.8/10 on the CVSS scale. 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 Source Code (All versions), TALON TC Compact (BACnet) (All versions < V3.5.4), TALON TC Modular (BACnet) (All versions < V3.5.4). FTP server does not properly validate the length of the “PWD/XPWD” command, leading to stack-based buffer overflows. EPSS estimates a 2.37% chance of exploitation in the next 30 days.

Description

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 Source Code (All versions), TALON TC Compact (BACnet) (All versions < V3.5.4), TALON TC Modular (BACnet) (All versions < V3.5.4). FTP server does not properly validate the length of the “PWD/XPWD” command, leading to stack-based buffer overflows. This may result in Denial-of-Service conditions and Remote Code Execution. (FSMD-2021-0016)

Metrics

CVSS 3.1

8.8/10

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

EPSS Probability

2.37%

81.7th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Siemens	Nucleus Net	All versions
Siemens	Nucleus Readystart V3	< 2017.02.4
Siemens	Nucleus Source Code	All versions
Siemens	Apogee Modular Building Controller Firmware	All versions
Siemens	Apogee Modular Equiment Controller Firmware	All versions
Siemens	Apogee Pxc Compact Firmware	< 2.8.19
Siemens	Apogee Pxc Compact Firmware	< 3.5.4
Siemens	Apogee Pxc Modular Firmware	< 2.8.19
Siemens	Apogee Pxc Modular Firmware	< 3.5.4
Siemens	Talon Tc Compact Firmware	< 3.5.4
Siemens	Talon Tc Modular Firmware	< 3.5.4
Siemens	Desigo Pxc00-E.D Firmware	>= 2.3, < 6.30.016
Siemens	Desigo Pxc00-U Firmware	>= 2.3, < 6.30.016
Siemens	Desigo Pxc001-E.D Firmware	>= 2.3, < 6.30.016
Siemens	Desigo Pxc12-E.D Firmware	>= 2.3, < 6.30.016
Siemens	Desigo Pxc22-E.D Firmware	>= 2.3, < 6.30.016
Siemens	Desigo Pxc22.1-E.D Firmware	>= 2.3, < 6.30.016
Siemens	Desigo Pxc36.1-E.D Firmware	>= 2.3, < 6.30.016
Siemens	Desigo Pxc50-E.D Firmware	>= 2.3, < 6.30.016
Siemens	Desigo Pxc64-U Firmware	>= 2.3, < 6.30.016
Siemens	Desigo Pxc100-E.D Firmware	>= 2.3, < 6.30.016
Siemens	Desigo Pxc128-U Firmware	>= 2.3, < 6.30.016
Siemens	Desigo Pxc200-E.D Firmware	>= 2.3, < 6.30.016
Siemens	Desigo Pxm20-E Firmware	>= 2.3, < 6.30.016

References

https://cert-portal.siemens.com/productcert/pdf/ssa-044112.pdfVendor Advisory
https://cert-portal.siemens.com/productcert/pdf/ssa-114589.pdfVendor Advisory
https://cert-portal.siemens.com/productcert/pdf/ssa-044112.pdfVendor Advisory
https://cert-portal.siemens.com/productcert/pdf/ssa-114589.pdfVendor Advisory

Timeline

Published: Nov 9, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-31887?

How severe is CVE-2021-31887?

CVE-2021-31887 has a CVSS score of 8.8/10 (HIGH severity). The EPSS model estimates a 2.37% probability of exploitation in the next 30 days.

How do I fix CVE-2021-31887?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-31887?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST