Siemens APOGEE/TALON Field Panels

1. EXECUTIVE SUMMARY

• CVSS v3 6.5
• ATTENTION: Exploitable remotely/low attack complexity
• Vendor: Siemens 
• Equipment: APOGEE PXC/TALON TC 
• Vulnerabilities: Predictable Exact Value from Previous Values

2. RISK EVALUATION

Successful exploitation of this vulnerability could allow an attacker to hijack existing sessions or spoof future sessions.

3. TECHNICAL DETAILS

3.1 AFFECTED PRODUCTS

The following products from Siemens are affected:

• APOGEE PXC Series (BACnet): All versions prior to 3.5.5
• APOGEE PXC Series (P2 Ethernet): All versions prior to 2.8.20
• TALON TC Series (BACnet): All versions prior to 3.5.5

3.2 VULNERABILITY OVERVIEW

3.2.1    PREDICTABLE EXACT VALUE FROM PREVIOUS VALUES CWE-342

Initial sequence numbers (ISNs) for TCP connections are derived from an insufficiently random source; the ISN of current and future TCP connections could be predictable. An attacker could hijack existing sessions or spoof future sessions.

CVE-2020-28388 has been assigned to this vulnerability. A CVSS v3 base score of 6.5 has been calculated. the CVSS vector string is (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L)

3.3 BACKGROUND

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

3.4 RESEARCHER

Siemens reported these vulnerabilities to CISA.

4. MITIGATIONS

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

• APOGEE PXC Series (P2 Ethernet): Update to V2.8.20 or later versions
• APOGEE PXC Series (BACnet): Update to V3.5.5 or later versions
• TALON TC Series (BACnet): Update to V3.5.5 or later versions

As a general security measure, Siemens strongly 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 to follow the recommendations in the product manuals.

For more information, see the associated Siemens security advisory SSA-408105 in HTML and CSAF.

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

• Minimize network exposure for all control system devices and/or systems, and ensure they are not accessible from the Internet.
• Locate control system networks and remote devices behind firewalls and isolate them from business networks.
• 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 at cisa.gov/ics. Several CISA products detailing cyber defense best 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 at cisa.gov/ics in the technical information paper, ICS-TIP-12-146-01B--Targeted Cyber Intrusion Detection and Mitigation Strategies.

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

No known public exploits specifically target this vulnerability. 

• Siemens