Siemens Nucleus RTOS TCP/IP Stack Improper Null Termination (CVE-2021-31884)

critical Tenable OT Security Plugin ID 500589

Synopsis

The remote OT asset is affected by a vulnerability.

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), Capital VSTAR (All versions with enabled Ethernet options), 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). The DHCP client application assumes that the data supplied with the Hostname DHCP option is NULL terminated. In cases when global hostname variable is not defined, this may lead to Out-of-bound reads, writes, and Denial-of-service conditions.
(FSMD-2021-0014)

This plugin only works with Tenable.ot.
Please visit https://www.tenable.com/products/tenable-ot for more information.

Solution

The following text was originally created by the Cybersecurity and Infrastructure Security Agency (CISA). The original can be found at CISA.gov.

Siemens has released updates for several of the affected products and recommends updating to the latest versions.
Siemens recommends countermeasures for products where updates are not available. Siemens has not identified any additional specific workarounds or mitigations.

- Capital VSTAR: Contact Siemens Customer Support to receive patch and update information.
- Nucleus NET: Update to the latest version of Nucleus ReadyStart v3 or v4. Contact Siemens Customer Support or a Nucleus sales team for mitigation advice.
- Nucleus ReadyStart v3: Update to v2017.02.4 or later version.
- Nucleus ReadyStart v4: Update to v4.1.1 or later version.
- Nucleus Source Code: Contact Siemens Customer Support to receive patch and update information.

As a general security measure, Siemens recommends protecting network access to devices with appropriate mechanisms. In order to operate the devices in a protected IT environment, Siemens recommends configuring the environment according to Siemens’ operational guidelines for industrial security and following the recommendations in the product manuals.

For additional information, please refer to Siemens Security Advisory SSA-044112

Plugin Details

Severity: Critical

ID: 500589

Version: 1.12

Type: remote

Family: Tenable.ot

Published: 2/7/2022

Updated: 6/6/2025

Supported Sensors: Tenable OT Security

Risk Information

VPR

Risk Factor: Medium

Score: 6.7

CVSS v2

Risk Factor: High

Base Score: 7.5

Temporal Score: 5.5

Vector: CVSS2#AV:N/AC:L/Au:N/C:P/I:P/A:P

CVSS Score Source: CVE-2021-31884

CVSS v3

Risk Factor: Critical

Base Score: 9.8

Temporal Score: 8.5

Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Temporal Vector: CVSS:3.0/E:U/RL:O/RC:C

Vulnerability Information

CPE: cpe:/o:siemens:apogee_modular_equiment_controller_firmware, cpe:/o:siemens:desigo_pxc200-e.d_firmware, cpe:/o:siemens:desigo_pxc64-u_firmware, cpe:/o:siemens:desigo_pxc128-u_firmware, cpe:/o:siemens:desigo_pxc22.1-e.d_firmware, cpe:/o:siemens:desigo_pxc36.1-e.d_firmware, cpe:/o:siemens:apogee_pxc_modular_firmware, cpe:/o:siemens:desigo_pxc100-e.d_firmware, cpe:/o:siemens:desigo_pxc001-e.d_firmware, cpe:/o:siemens:desigo_pxc00-e.d_firmware, cpe:/o:siemens:desigo_pxc22-e.d_firmware, cpe:/o:siemens:desigo_pxm20-e_firmware, cpe:/o:siemens:desigo_pxc12-e.d_firmware, cpe:/o:siemens:apogee_modular_building_controller_firmware, cpe:/o:siemens:apogee_pxc_compact_firmware, cpe:/o:siemens:desigo_pxc00-u_firmware, cpe:/o:siemens:desigo_pxc50-e.d_firmware

Required KB Items: Tenable.ot/Siemens

Exploit Ease: No known exploits are available

Patch Publication Date: 11/9/2021

Vulnerability Publication Date: 11/9/2021

Reference Information

CVE: CVE-2021-31884

CWE: 170

ICSA: 21-313-03, 21-315-07

Detections

Analytics