-----BEGIN PGP SIGNED MESSAGE-----
AUSCERT External Security Bulletin Redistribution
Advisory (icsa-21-257-07) Siemens APOGEE and TALON
15 September 2021
AusCERT Security Bulletin Summary
Product: Siemens APOGEE
Operating System: Network Appliance
Impact/Access: Root Compromise -- Remote/Unauthenticated
Execute Arbitrary Code/Commands -- Remote/Unauthenticated
CVE Names: CVE-2021-27391
- --------------------------BEGIN INCLUDED TEXT--------------------
ICS Advisory (ICSA-21-257-07)
Siemens APOGEE and TALON
Original release date: September 14, 2021
All information products included in https://us-cert.cisa.gov/ics are provided
"as is" for informational purposes only. The Department of Homeland Security
(DHS) does not provide any warranties of any kind regarding any information
contained within. DHS does not endorse any commercial product or service,
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
information about TLP, see https://us-cert.cisa.gov/tlp/ .
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')
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/
o CRITICAL INFRASTRUCTURE SECTORS: Critical Manufacturing
o COUNTRIES/AREAS DEPLOYED: Worldwide
o COMPANY HEADQUARTERS LOCATION: Germany
Paul Noalhyt and David Doggett from Red Balloon Security reported this
vulnerability to Siemens.
Siemens recommends updating the following products to v3.5.3 or later (login
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
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
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
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:
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.
- --------------------------END INCLUDED TEXT--------------------
You have received this e-mail bulletin as a result of your organisation's
registration with AusCERT. The mailing list you are subscribed to is
maintained within your organisation, so if you do not wish to continue
receiving these bulletins you should contact your local IT manager. If
you do not know who that is, please send an email to email@example.com
and we will forward your request to the appropriate person.
NOTE: Third Party Rights
This security bulletin is provided as a service to AusCERT's members. As
AusCERT did not write the document quoted above, AusCERT has had no control
over its content. The decision to follow or act on information or advice
contained in this security bulletin is the responsibility of each user or
organisation, and should be considered in accordance with your organisation's
site policies and procedures. AusCERT takes no responsibility for consequences
which may arise from following or acting on information or advice contained in
this security bulletin.
NOTE: This is only the original release of the security bulletin. It may
not be updated when updates to the original are made. If downloading at
a later date, it is recommended that the bulletin is retrieved directly
from the author's website to ensure that the information is still current.
Contact information for the authors of the original document is included
in the Security Bulletin above. If you have any questions or need further
information, please contact them directly.
Previous advisories and external security bulletins can be retrieved from:
Australian Computer Emergency Response Team
The University of Queensland
Internet Email: firstname.lastname@example.org
Facsimile: (07) 3365 7031
Telephone: (07) 3365 4417 (International: +61 7 3365 4417)
AusCERT personnel answer during Queensland business hours
which are GMT+10:00 (AEST).
On call after hours for member emergencies only.
-----BEGIN PGP SIGNATURE-----
-----END PGP SIGNATURE-----