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             AUSCERT External Security Bulletin Redistribution

                               ESB-2021.3107
            Advisory (icsa-21-257-07) Siemens APOGEE and TALON
                             15 September 2021

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        AusCERT Security Bulletin Summary
        ---------------------------------

Product:           Siemens APOGEE
                   Siemens TALON
Publisher:         ICS-CERT
Operating System:  Network Appliance
Impact/Access:     Root Compromise                 -- Remote/Unauthenticated
                   Execute Arbitrary Code/Commands -- Remote/Unauthenticated
Resolution:        Patch/Upgrade
CVE Names:         CVE-2021-27391  

Original Bulletin: 
   https://us-cert.cisa.gov/ics/advisories/icsa-21-257-07

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ICS Advisory (ICSA-21-257-07)

Siemens APOGEE and TALON

Original release date: September 14, 2021

Legal Notice

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"as is" for informational purposes only. The Department of Homeland Security
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referenced in this product or otherwise. Further dissemination of this product
is governed by the Traffic Light Protocol (TLP) marking in the header. For more
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1. EXECUTIVE SUMMARY

  o CVSS v3 9.8
  o ATTENTION: Exploitable remotely/low attack complexity
  o Vendor: Siemens
  o Equipment: APOGEE and TALON
  o Vulnerability: Classic Buffer Overflow

2. RISK EVALUATION

Successful exploitation of this vulnerability could allow an attacker to
execute arbitrary code on the device with root privileges.

3. TECHNICAL DETAILS

3.1 AFFECTED PRODUCTS

The following products are affected:

  o APOGEE MBC (PPC) (P2 Ethernet): v2.6.3 and newer
  o APOGEE MEC (PPC) (P2 Ethernet): v2.6.3 and newer
  o APOGEE PXC Compact (BACnet): All versions prior to v3.5.3
  o APOGEE PXC Compact (P2 Ethernet): v2.8 and newer
  o APOGEE PXC Modular (BACnet): All versions prior to v3.5.3
  o APOGEE PXC Modular (P2 Ethernet): v2.8 and newer
  o TALON TC Compact (BACnet): All versions prior to v3.5.3
  o TALON TC Modular (BACnet): All versions prior to v3.5.3

3.2 VULNERABILITY OVERVIEW

3.2.1 BUFFER COPY WITHOUT CHECKING SIZE OF INPUT ('CLASSIC BUFFER OVERFLOW')
CWE-120

The web server of affected devices lacks proper bounds checking when parsing
specific requests, which could lead to a buffer overflow. An unauthenticated
remote attacker could exploit this vulnerability to execute arbitrary code on
the device with root privileges.

CVE-2021-27391 has been assigned to this vulnerability. A CVSS v3 base score of
9.8 has been calculated; the CVSS vector string is ( AV:N/AC:L/PR:N/UI:N/S:U/
C:H/I:H/A:H ).

3.3 BACKGROUND

  o CRITICAL INFRASTRUCTURE SECTORS: Critical Manufacturing
  o COUNTRIES/AREAS DEPLOYED: Worldwide
  o COMPANY HEADQUARTERS LOCATION: Germany

3.4 RESEARCHER

Paul Noalhyt and David Doggett from Red Balloon Security reported this
vulnerability to Siemens.

4. MITIGATIONS

Siemens recommends updating the following products to v3.5.3 or later (login
required):

  o APOGEE PXC Compact (BACnet)
  o APOGEE PXC Modular (BACnet)
  o TALON TC Compact (BACnet)
  o TALON TC Modular (BACnet)

For products not listed above Siemens has recommended the following workarounds
and mitigations:

  o Contact a Siemens office for support.
  o Restrict access to the device, especially to the web interface. 80/TCP and
    443/TCP should only be connected to trusted IP addresses.
  o Disable the integrated web server.

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

For more information see Siemens Security Advisory SSA-944498

CISA recommends users take defensive measures to minimize the risk of
exploitation of this vulnerability. Specifically, users should:

  o Minimize network exposure for all control system devices and/or systems,
    and ensure that they are not accessible from the Internet .
  o Locate control system networks and remote devices behind firewalls, and
    isolate them from the business network.
  o When remote access is required, use secure methods, such as Virtual Private
    Networks (VPNs), recognizing VPNs may have vulnerabilities and should be
    updated to the most current version available. Also recognize VPN is only
    as secure as its connected devices.

CISA reminds organizations to perform proper impact analysis and risk
assessment prior to deploying defensive measures.

CISA also provides a section for control systems security recommended practices
on the ICS webpage on us-cert.cisa.gov . Several recommended practices are
available for reading and download, including Improving Industrial Control
Systems Cybersecurity with Defense-in-Depth Strategies .

Additional mitigation guidance and recommended practices are publicly available
on the ICS webpage on us-cert.cisa.gov in the Technical Information Paper,
ICS-TIP-12-146-01B--Targeted Cyber Intrusion Detection and Mitigation
Strategies .

Organizations observing any suspected malicious activity should follow their
established internal procedures and report their findings to CISA for tracking
and correlation against other incidents.

No known public exploits specifically target this vulnerability.

For any questions related to this report, please contact the CISA at:

Email: CISAservicedesk@cisa.dhs.gov
Toll Free: 1-888-282-0870

CISA continuously strives to improve its products and services. You can help by
choosing one of the links below to provide feedback about this product.

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