ICS Advisory (ICSA-21-336-01)

Schneider Electric SESU

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  • CVSS v3 3.8
  • ATTENTION: Low attack complexity
  • Vendor: Schneider Electric
  • Equipment: Schneider Electric Software Update (SESU)
  • Vulnerability: Insufficient Entropy


Successful exploitation of this vulnerability could cause unintended connection from an internal network to an external network.



The following versions of Schneider Electric Software Update, are affected:

  • Schneider Electric Software Update: v2.3.0 through v2.5.1

Schneider Electric Software Update is used by the following products:

  • EcoStruxure Augmented Operator Advisor
  • EcoStruxure Control Expert (formerly known as Unity Pro)
  • EcoStruxure Process Expert (formerly known as EcoStruxure Hybrid Distributed Control System)
  • EcoStruxure Machine Expert (formerly known as SoMachine or SoMachine Motion)
  • EcoStruxure Machine Expert Basic
  • EcoStruxure Operator Terminal Expert
  • EcoStruxure Plant Builder
  • EcoStruxure Power Design
  • EcoStruxure Automation Expert
  • EcoStruxure Automation Maintenance Expert
  • Eurotherm Data Reviewer
  • Eurotherm iTools
  • eXLhoist Configuration Software
  • Schneider Electric Floating License Manager
  • Schneider Electric License Manager 
  • Harmony XB5SSoft
  • SoMove
  • Versatile Software BLUE
  • Vijeo Designer
  • OsiSense XX Configuration Software
  • Zelio Soft 2

Note: This vulnerability affects all products listed above, but this is not a complete list of products. Some of the products might not deliver SESU as part of the product package; however, SESU can be downloaded and used to manage product updates. It may also be possible more components for one product are listed in the “SESU Managed Products” dialog for update.



An insufficient entropy vulnerability exists, which could cause unintended connection from an internal network to an external network when an attacker manages to decrypt the SESU proxy password from the registry.

CVE-2021-22799 has been assigned to this vulnerability. A CVSS v3 base score of 3.8 has been calculated; the CVSS vector string is (AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:N/A:N).


  • CRITICAL INFRASTRUCTURE SECTORS: Commercial Facilities, Critical Manufacturing, Energy


Nozomi Networks reported this vulnerability to CISA.


Schneider Electric recommends the following:

  • If SESU is installed (assuming SESU is configured as “managed product” inside the SESU application) it will indicate a security update is available. Click to download and install the new SESU version.
  • If SESU is not installed, download SESU (automatic download) and follow the installation instructions.

Schneider Electric strongly recommends observing the following industry cybersecurity best practices:

  • Locate control and safety system networks and remote devices behind firewalls and isolate them from the business network.
  • Install physical controls so no unauthorized personnel can access your industrial control and safety systems, components, peripheral equipment, and networks.
  • Place all controllers in locked cabinets and never leave them in the “Program” mode.
  • Never connect programming software to any network other than the network intended for that device.
  • Scan all methods of mobile data exchange with the isolated network such as CDs, USB drives, etc. before use in the terminals or any node connected to these networks.
  • Never allow mobile devices that have connected to any other network besides the intended network to connect to the safety or control networks without proper sanitation.
  • Minimize network exposure for all control system devices and systems and ensure they are not accessible from the Internet.
  • 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 are only as secure as the connected devices.

See Schneider Electric Security Notification SEVD-2021-313-02 for more information.

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. This vulnerability is not exploitable remotely.

Contact Information

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

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

For industrial control systems cybersecurity information:  https://us-cert.cisa.gov/ics 
or incident reporting:  https://us-cert.cisa.gov/report

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