1. EXECUTIVE SUMMARY

  • CVSS v3 7.5
  • ATTENTION: Exploitable remotely/low skill level to exploit
  • Vendor: Siemens
  • Equipment: SIMATIC PCS 7, SIMATIC WinCC, SIMATIC NET PC
  • Vulnerability: Incorrect Calculation of Buffer Size

2. UPDATE INFORMATION

This updated advisory is a follow-up to the advisory update titled 20-042-06 Siemens SIMATIC PCS 7, SIMATIC WinCC, and SIMATIC NET PC that (Update B) was published April 14, 2020, to the ICS webpage on us-cert.gov. 

3. RISK EVALUATION

Successful exploitation of this vulnerability could allow an attacker with network access to cause a denial-of-service condition.

4. TECHNICAL DETAILS

4.1 AFFECTED PRODUCTS

The following versions of SIMATIC software are affected:

  • OpenPCS 7 v8.1 all versions
  • OpenPCS 7 v8.2 all versions
  • OpenPCS 7 v9.0 all versions
  • SIMATIC BATCH v8.1 all versions
  • SIMATIC BATCH v8.2 all versions
  • SIMATIC BATCH v9.0 all versions
  • SIMATIC NET PC Software all versions
  • SIMATIC PCS 7 v8.1 all versions
  • SIMATIC PCS 7 v8.2 all versions 
  • SIMATIC PCS 7 v9.0 all versions
  • SIMATIC Route Control v8.1 all versions
  • SIMATIC Route Control v8.2 all versions
  • SIMATIC Route Control v9.0 all versions
  • SIMATIC WinCC (TIA Portal) v13 all versions prior to v13 SP2
  • SIMATIC WinCC (TIA Portal) v14.0.1 all versions
  • SIMATIC WinCC (TIA Portal) v15.1 all versions
  • SIMATIC WinCC (TIA Portal) v16 all versions
  • SIMATIC WinCC v7.3 all versions
  • SIMATIC WinCC v7.4 all versions
  • SIMATIC WinCC v7.5 all versions prior to v7.5.1 Upd1

4.2 VULNERABILITY OVERVIEW

4.2.1    INCORRECT CALCULATION OF BUFFER SIZE CWE-131

Through specially crafted messages, when encrypted communication is enabled, an attacker with network access could compromise the availability of the system by causing a denial-of-service condition.

CVE-2019-19282 has been assigned to this vulnerability. A CVSS v3 base score of 7.5 has been assigned; the CVSS vector string is (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H).

4.3 BACKGROUND

  • CRITICAL INFRASTRUCTURE SECTORS: Chemical, Critical Manufacturing, Energy, Food and Agriculture, Water and Wastewater Systems
  • COUNTRIES/AREAS DEPLOYED: Worldwide
  • COMPANY HEADQUARTERS LOCATION: Germany

4.4 RESEARCHER

Nicholas Miles from Tenable reported this vulnerability to Siemens.

5. MITIGATIONS

Siemens has identified the following specific workarounds and mitigations:

  • Apply cell protection concept
  • Use VPN for protecting network communication between cells
  • Apply Defense-in-Depth
  • For SIMATIC NET PC Software, Siemens recommends affected users update to v16 update 1 or higher.
  • For SIMATIC WinCC (TIA Portal) v13, Siemens recommends affected users update to v13 SP2 or higher. 
  • For SIMATIC WinCC (TIA Portal) v16, Siemens recommends affected users update to v16 update 1 or higher.

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——— End Update C Part 1 of 1 ———

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

Source:

https://www.us-cert.gov/ics/advisories/icsa-20-042-06