1. EXECUTIVE SUMMARY
- CVSS v3 7.5
- ATTENTION: Exploitable remotely/low skill level to exploit
- Vendor: Schneider Electric
- Equipment: PLC Simulator for EcoStruxure Control Expert
- Vulnerability: Improper Check for Unusual or Exceptional Conditions
2. RISK EVALUATION
Successful exploitation of this vulnerability could cause a denial-of-service condition, which could result in a failure of the EcoStruxture Control Expert Simulator.
3. TECHNICAL DETAILS
3.1 AFFECTED PRODUCTS
Schneider Electric reports the vulnerability affects the following PLC simulators:
- PLC Simulator for EcoStruxure Control Expert, all versions
- PLC Simulator for Unity Pro (former name of EcoStruxure Control Expert), all versions
3.2 VULNERABILITY OVERVIEW
3.2.1 IMPROPER CHECK FOR UNUSUAL OR EXCEPTIONAL CONDITIONS CWE-754
A vulnerability exists that could cause a crash of the PLC simulator present in EcoStruxure Control Expert software when receiving a specially crafted request over Modbus.
CVE-2020-7538 has been assigned to this vulnerability. A CVSS v3 base score of 7.5 has been calculated; the CVSS vector string is (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H).
3.3 BACKGROUND
- CRITICAL INFRASTRUCTURE SECTORS: Commercial Facilities, Energy, Food and Agriculture, Government Facilities, Transportation Systems, Water and Wastewater Systems
- COUNTRIES/AREAS DEPLOYED: Worldwide
- COMPANY HEADQUARTERS LOCATION: France
3.4 RESEARCHER
Parity Dynamics Research Team reported this vulnerability to CISA.
4. MITIGATIONS
Schneider Electric has released Version 15.0 of the EcoStruxure Control Expert software to mitigate this vulnerability. It is available for download on the Schneider Electric website.
After downloading the fix, the following step is required to mitigate the vulnerability:
- In the option dialog box of the PLC simulator, set the listening IP Address to 127.0.0.1 (localhost), which will prevent remote network connections to the PLC simulator.
The default listening IP address is: 0.0.0.0. The default setting exposes the PLC to the vulnerability described in this advisory.
Schneider Electric recommends using appropriate patching methodologies when applying these patches. It also strongly recommends the use of back-ups and evaluating the impact of these patches in a test and development environment or on offline infrastructure. Contact Schneider Electric’s Customer Care Center for assistance removing a patch.
If users choose not to apply the remediation provided above, they should immediately apply the following mitigations to reduce the risk of exploit:
- Set up network segmentation and implement a firewall to block all unauthorized access to Port 502/TCP
- Harden the engineering workstation running PLC Simulator for EcoStruxure Control Expert
- Follow workstation, network, and site-hardening guidelines in the Cybersecurity Best Practices guide.
Please see Schneider Electric Security Notification number SEVD-2020-315-07 for more information.
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.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.
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