CVE-2025-3112 Schneider Electric CVE debrief

Who should care

Industrial control system operators, Schneider Electric Modicon M241/M251 administrators, and OT security teams responsible for devices where the controller webserver is enabled or reachable. Organizations using EcoStruxure Machine Expert or EcoStruxure Automation Expert - Motion for firmware updates should also review the remediation path.

Technical summary

CVE-2025-3112 affects Schneider Electric Modicon Controllers M241 and M251 versions prior to 5.3.12.51. The issue is classified as CWE-400 (Uncontrolled Resource Consumption). The supplied advisory says an authenticated attacker with low privileges can manipulate the HTTPS Content-Length header sent to the webserver and trigger a denial of service. CISA lists the CVSS v3.1 vector as AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H (6.5 medium).

Defensive priority

Medium; prioritize remediation for any M241/M251 deployment where the webserver is enabled or exposed to broader network access.

Recommended defensive actions

• Update Modicon Controllers M241 to version 5.3.12.51 and reboot after applying the fix using EcoStruxure Automation Expert - Motion v24.1 or EcoStruxure Machine Expert v2.3 as directed by the vendor advisory.
• Update Modicon Controllers M251 to version 5.3.12.51 and reboot after applying the fix using EcoStruxure Automation Expert - Motion v24.1 or EcoStruxure Machine Expert v2.3 as directed by the vendor advisory.
• If you cannot remediate immediately, deactivate the webserver when it is not needed.
• Restrict access to the controllers by using protected environments, network segmentation, and firewall rules that block unauthorized access to ports 80/HTTP and 443/HTTPS.
• Use VPN tunnels for remote access, keep user management enabled, and use strong passwords.
• Use encrypted communication links and follow Schneider Electric's product-specific hardening guidance for Modicon and associated equipment.

Evidence notes

Primary evidence comes from CISA CSAF advisory ICSA-25-175-03 (published 2025-06-10, revised 2025-07-08). The advisory identifies Schneider Electric Modicon Controllers M241 and M251 as affected products, with versions prior to 5.3.12.51 impacted, and states that remediation is available in 5.3.12.51. The provided description and CVSS vector indicate a network-reachable denial-of-service condition requiring low-privilege authentication, caused by manipulated HTTPS Content-Length handling in the webserver. The revision history shows the July update added remediation availability via EcoStruxure Machine Expert v2.3 for updating M241/M251 firmware.

Official resources