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# SSA-114589: Multiple Vulnerabilities in Nucleus RTOS based APOGEE, TALON and Desigo
PXC/PXM Products

Publication Date:        2021-11-09
Last Update:             2022-05-10
Current Version:         1.3
CVSS v3.1 Base Score:    9.8

SUMMARY
=======

Multiple vulnerabilities (also known as "NUCLEUS:13") have been
identified in the Nucleus RTOS (real-time operating system) and reported
in the Siemens Security Advisory SSA-044112:
https://cert-portal.siemens.com/productcert/pdf/ssa-044112.pdf.

The products listed below use affected versions of the Nucleus software
and inherently contain these vulnerabilities.

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


AFFECTED PRODUCTS AND SOLUTION
==============================


* APOGEE MBC (PPC) (BACnet)
  - Affected versions:
       All versions
  - Remediation:
       Currently no fix is planned
       See recommendations from section "Workarounds and Mitigations"

* APOGEE MBC (PPC) (P2 Ethernet)
  - Affected versions:
       All versions
  - Remediation:
       Currently no fix is planned
       See recommendations from section "Workarounds and Mitigations"

* APOGEE MEC (PPC) (BACnet)
  - Affected versions:
       All versions
  - Remediation:
       Currently no fix is planned
       See recommendations from section "Workarounds and Mitigations"

* APOGEE MEC (PPC) (P2 Ethernet)
  - Affected versions:
       All versions
  - Remediation:
       Currently no fix is planned
       See recommendations from section "Workarounds and Mitigations"

* APOGEE PXC Compact (BACnet)
  - Affected versions:
       All versions < V3.5.4
  - Remediation:
       Update to V3.5.4 or later version
       See further recommendations from section "Workarounds and Mitigations"

* APOGEE PXC Compact (P2 Ethernet)
  - Affected versions:
       All versions < V2.8.19
  - Remediation:
       Update to V2.8.19 or later version
       See further recommendations from section "Workarounds and Mitigations"

* APOGEE PXC Modular (BACnet)
  - Affected versions:
       All versions < V3.5.4
  - Remediation:
       Update to V3.5.4 or later version
       See further recommendations from section "Workarounds and Mitigations"

* APOGEE PXC Modular (P2 Ethernet)
  - Affected versions:
       All versions < V2.8.19
  - Remediation:
       Update to V2.8.19 or later version
       See further recommendations from section "Workarounds and Mitigations"

* Desigo PXC00-E.D
  - Affected versions:
       All versions >= V2.3 and < V6.30.016
  - Remediation:
       Update to V6.30.016 or later version
       See further recommendations from section "Workarounds and Mitigations"
  - Download:
       https://support.industry.siemens.com/cs/ww/en/view/109810577

* Desigo PXC00-U
  - Affected versions:
       All versions >= V2.3 and < V6.30.016
  - Remediation:
       Update to V6.30.016 or later version
       See further recommendations from section "Workarounds and Mitigations"
  - Download:
       https://support.industry.siemens.com/cs/ww/en/view/109810577

* Desigo PXC001-E.D
  - Affected versions:
       All versions >= V2.3 and < V6.30.016
  - Remediation:
       Update to V6.30.016 or later version
       See further recommendations from section "Workarounds and Mitigations"
  - Download:
       https://support.industry.siemens.com/cs/ww/en/view/109810577

* Desigo PXC12-E.D
  - Affected versions:
       All versions >= V2.3 and < V6.30.016
  - Remediation:
       Update to V6.30.016 or later version
       See further recommendations from section "Workarounds and Mitigations"
  - Download:
       https://support.industry.siemens.com/cs/ww/en/view/109810577

* Desigo PXC22-E.D
  - Affected versions:
       All versions >= V2.3 and < V6.30.016
  - Remediation:
       Update to V6.30.016 or later version
       See further recommendations from section "Workarounds and Mitigations"
  - Download:
       https://support.industry.siemens.com/cs/ww/en/view/109810577

* Desigo PXC22.1-E.D
  - Affected versions:
       All versions >= V2.3 and < V6.30.016
  - Remediation:
       Update to V6.30.016 or later version
       See further recommendations from section "Workarounds and Mitigations"
  - Download:
       https://support.industry.siemens.com/cs/ww/en/view/109810577

* Desigo PXC36.1-E.D
  - Affected versions:
       All versions >= V2.3 and < V6.30.016
  - Remediation:
       Update to V6.30.016 or later version
       See further recommendations from section "Workarounds and Mitigations"
  - Download:
       https://support.industry.siemens.com/cs/ww/en/view/109810577

* Desigo PXC50-E.D
  - Affected versions:
       All versions >= V2.3 and < V6.30.016
  - Remediation:
       Update to V6.30.016 or later version
       See further recommendations from section "Workarounds and Mitigations"
  - Download:
       https://support.industry.siemens.com/cs/ww/en/view/109810577

* Desigo PXC64-U
  - Affected versions:
       All versions >= V2.3 and < V6.30.016
  - Remediation:
       Update to V6.30.016 or later version
       See further recommendations from section "Workarounds and Mitigations"
  - Download:
       https://support.industry.siemens.com/cs/ww/en/view/109810577

* Desigo PXC100-E.D
  - Affected versions:
       All versions >= V2.3 and < V6.30.016
  - Remediation:
       Update to V6.30.016 or later version
       See further recommendations from section "Workarounds and Mitigations"
  - Download:
       https://support.industry.siemens.com/cs/ww/en/view/109810577

* Desigo PXC128-U
  - Affected versions:
       All versions >= V2.3 and < V6.30.016
  - Remediation:
       Update to V6.30.016 or later version
       See further recommendations from section "Workarounds and Mitigations"
  - Download:
       https://support.industry.siemens.com/cs/ww/en/view/109810577

* Desigo PXC200-E.D
  - Affected versions:
       All versions >= V2.3 and < V6.30.016
  - Remediation:
       Update to V6.30.016 or later version
       See further recommendations from section "Workarounds and Mitigations"
  - Download:
       https://support.industry.siemens.com/cs/ww/en/view/109810577

* Desigo PXM20-E
  - Affected versions:
       All versions >= V2.3 and < V6.30.016
  - Remediation:
       Update to V6.30.016 or later version
       See further recommendations from section "Workarounds and Mitigations"
  - Download:
       https://support.industry.siemens.com/cs/ww/en/view/109810577

* TALON TC Compact (BACnet)
  - Affected versions:
       All versions < V3.5.4
  - Remediation:
       Update to V3.5.4 or later version
       See further recommendations from section "Workarounds and Mitigations"

* TALON TC Modular (BACnet)
  - Affected versions:
       All versions < V3.5.4
  - Remediation:
       Update to V3.5.4 or later version
       See further recommendations from section "Workarounds and Mitigations"


WORKAROUNDS AND MITIGATIONS
===========================

Siemens has identified the following specific workarounds and mitigations that
customers can apply to reduce the risk:

* CVE-2021-31881, CVE-2021-31882, CVE-2021-31883, CVE-2021-31884: Disable
the DHCP client and use static IP address configuration instead (Note
that the DHCP client is disabled by default on APOGEE/TALON and Desigo
products.)

* CVE-2021-31885, CVE-2021-31886, CVE-2021-31887, CVE-2021-31888: Disable
the FTP service (Note that the FTP service is disabled by default on
Desigo products.)


Product specific remediations or mitigations can be found in the section
"Affected Products and Solution".

Please follow the "General Security Recommendations".


GENERAL SECURITY RECOMMENDATIONS
================================

As a general security measure Siemens strongly recommends to protect
network access to affected products with appropriate mechanisms. It is
advised to follow recommended security practices in order to run the
devices in a protected IT environment.

PRODUCT DESCRIPTION
===================

The APOGEE MEC and the MBC are high-performance Direct Digital Control
(DDC) devices and are an integral part of the APOGEE Automation System.

The APOGEE PXC Modular and Compact Series are high-performance Direct
Digital Control (DDC) devices and an integral part of the APOGEE
Automation System.

The Desigo PX automation stations and operator units control and monitor
building automation systems. They allow for alarm signaling, time-based
programs and trend logging.

The TALON TC Modular and Compact Series are high-performance Direct
Digital Control (DDC) devices and an integral part of the TALON
Automation System.

VULNERABILITY CLASSIFICATION
============================

The vulnerability classification has been performed by using the CVSS scoring
system in version 3.1 (CVSS v3.1) (https://www.first.org/cvss/). The CVSS
environmental score is specific to the customer's environment and will impact
the overall CVSS score. The environmental score should therefore be
individually defined by the customer to accomplish final scoring.

An additional classification has been performed using the CWE classification, a
community-developed list of common software security weaknesses. This serves as
a common language and as a baseline for weakness identification, mitigation,
and prevention efforts. A detailed list of CWE classes can be found at:
https://cwe.mitre.org/.



* Vulnerability CVE-2021-31344

  ICMP echo packets with fake IP options allow sending ICMP echo reply
  messages to arbitrary hosts on the network. (FSMD-2021-0004)

  CVSS v3.1 Base Score: 5.3
  CVSS Vector:          CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N/E:P/RL:O/RC:C
  CWE:                  CWE-843: Access of Resource Using Incompatible Type ('Type Confusion')

* Vulnerability CVE-2021-31345

  The total length of an UDP payload (set in the IP header) is unchecked.
  This may lead to various side effects, including Information Leak and
  Denial-of-Service conditions, depending on a user-defined applications
  that runs on top of the UDP protocol. (FSMD-2021-0006)

  CVSS v3.1 Base Score: 7.5
  CVSS Vector:          CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N/E:P/RL:O/RC:C
  CWE:                  CWE-1284: Improper Validation of Specified Quantity in Input

* Vulnerability CVE-2021-31346

  The total length of an ICMP payload (set in the IP header) is unchecked.
  This may lead to various side effects, including Information Leak and
  Denial-of-Service conditions, depending on the network buffer
  organization in memory. (FSMD-2021-0007)

  CVSS v3.1 Base Score: 8.2
  CVSS Vector:          CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H/E:P/RL:O/RC:C
  CWE:                  CWE-1284: Improper Validation of Specified Quantity in Input

* Vulnerability CVE-2021-31881

  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)

  CVSS v3.1 Base Score: 7.1
  CVSS Vector:          CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H/E:P/RL:O/RC:C
  CWE:                  CWE-125: Out-of-bounds Read

* Vulnerability CVE-2021-31882

  The DHCP client application does not validate the length of the Domain
  Name Server IP option(s) (0x06) when processing DHCP ACK packets. This
  may lead to Denial-of-Service conditions. (FSMD-2021-0011)

  CVSS v3.1 Base Score: 6.5
  CVSS Vector:          CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:P/RL:O/RC:C
  CWE:                  CWE-119: Improper Restriction of Operations within the Bounds of a Memory Buffer

* Vulnerability CVE-2021-31883

  When processing a DHCP ACK message, the DHCP client application does not
  validate the length of the Vendor option(s), leading to
  Denial-of-Service conditions. (FSMD-2021-0013)

  CVSS v3.1 Base Score: 7.1
  CVSS Vector:          CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H/E:P/RL:O/RC:C
  CWE:                  CWE-119: Improper Restriction of Operations within the Bounds of a Memory Buffer

* Vulnerability CVE-2021-31884

  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)

  CVSS v3.1 Base Score: 8.8
  CVSS Vector:          CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:P/RL:O/RC:C
  CWE:                  CWE-170: Improper Null Termination

* Vulnerability CVE-2021-31885

  TFTP server application allows for reading the contents of the TFTP
  memory buffer via sending malformed TFTP commands. (FSMD-2021-0009)

  CVSS v3.1 Base Score: 7.5
  CVSS Vector:          CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N/E:P/RL:O/RC:C
  CWE:                  CWE-805: Buffer Access with Incorrect Length Value

* Vulnerability CVE-2021-31886

  FTP server does not properly validate the length of the "USER" command,
  leading to stack-based buffer overflows. This may result in
  Denial-of-Service conditions and Remote Code Execution. (FSMD-2021-0010)

  CVSS v3.1 Base Score: 9.8
  CVSS Vector:          CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:P/RL:O/RC:C
  CWE:                  CWE-170: Improper Null Termination

* Vulnerability CVE-2021-31887

  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)

  CVSS v3.1 Base Score: 8.8
  CVSS Vector:          CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:P/RL:O/RC:C
  CWE:                  CWE-170: Improper Null Termination

* Vulnerability CVE-2021-31888

  FTP server does not properly validate the length of the "MKD/XMKD"
  command, leading to stack-based buffer overflows. This may result in
  Denial-of-Service conditions and Remote Code Execution. (FSMD-2021-0018)

  CVSS v3.1 Base Score: 8.8
  CVSS Vector:          CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:P/RL:O/RC:C
  CWE:                  CWE-170: Improper Null Termination

* Vulnerability CVE-2021-31889

  Malformed TCP packets with a corrupted SACK option leads to Information
  Leaks and Denial-of-Service conditions. (FSMD-2021-0015)

  CVSS v3.1 Base Score: 7.5
  CVSS Vector:          CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:P/RL:O/RC:C
  CWE:                  CWE-191: Integer Underflow (Wrap or Wraparound)

* Vulnerability CVE-2021-31890

  The total length of an TCP payload (set in the IP header) is unchecked.
  This may lead to various side effects, including Information Leak and
  Denial-of-Service conditions, depending on the network buffer
  organization in memory. (FSMD-2021-0017)

  CVSS v3.1 Base Score: 7.5
  CVSS Vector:          CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:P/RL:O/RC:C
  CWE:                  CWE-240: Improper Handling of Inconsistent Structural Elements




ADDITIONAL INFORMATION
======================
Siemens is working to develop a solution to resolve the issues
identified with the emphasis on addressing vulnerabilities that do not
have a specific mitigation first.

Products listed in this advisory use the Nucleus RTOS (Real-time
operating system).

For more details regarding the vulnerabilities reported for Nucleus RTOS
refer to Siemens Security Advisory SSA-044112:
https://cert-portal.siemens.com/productcert/pdf/ssa-044112.pdf

For further inquiries on security vulnerabilities in Siemens products and
solutions, please contact the Siemens ProductCERT:

https://www.siemens.com/cert/advisories


HISTORY DATA
============

V1.0 (2021-11-09): Publication Date
V1.1 (2021-12-14): Added affected Desigo PXC/PXM products; updated corresponding mitigation
measures; informed about planned solutions
V1.2 (2022-04-12): Added solutions for APOGEE PXC Compact (BACnet), APOGEE PXC Modular
(BACnet), TALON TC Compact (BACnet), and TALON TC Modular (BACnet)
products
V1.3 (2022-05-10): Added solutions for APOGEE PXC Compact (P2 Ethernet), APOGEE PXC Modular
(P2 Ethernet), Desigo PXC Products, Desigo PXM Products

TERMS OF USE
============

Siemens Security Advisories are subject to the terms and conditions contained
in Siemens' underlying license terms or other applicable agreements previously
agreed to with Siemens (hereinafter "License Terms"). To the extent applicable
to information, software or documentation made available in or through a
Siemens Security Advisory, the Terms of Use of Siemens' Global Website
(https://www.siemens.com/terms_of_use, hereinafter "Terms of Use"), in
particular Sections 8-10 of the Terms of Use, shall apply additionally. In case
of conflicts, the License Terms shall prevail over the Terms of Use.

Copyright: Siemens 2022
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