CVE-2025-13902: Patching Schneider Electric Modicon Controllers

Schneider Electric has released a security advisory concerning several models of its Modicon logic controllers. According to ICSA-26-078-02, a vulnerability identified as CVE-2025-13902 exists within the web interface of these devices. This flaw, discovered by researcher Noam Moshe of Claroty, allows for Improper Neutralization of Input During Web Page Generation, a class of vulnerability commonly referred to as XSS.

Technical Analysis of CVE-2025-13902

The CVE is characterized by a failure to sanitize user-supplied input effectively before rendering it within the browser of an authenticated user. Specifically, the vulnerability enables an attacker with existing credentials to inject a malicious payload into the web server. When a victim subsequently interacts with the web interface—specifically by hovering over a crafted element—the browser executes arbitrary JavaScript.

While the CVSS base score is 5.4, indicating a medium severity, the impact on industrial environments is noteworthy. Because the flaw requires an authenticated session, the primary threat arises from lateral movement or Phishing attacks where an internal user is targeted. Successful exploitation can lead to an account takeover scenario, permitting an adversary to hijack the session of an engineer or administrator and potentially modify controller logic or operational parameters.

Schneider Electric Modicon M241 Firmware Update Guide

For organizations utilizing the affected hardware, immediate remediation is required to prevent unauthorized access. The following versions are confirmed as affected:

• Modicon M241: All versions prior to 5.4.13.12
• Modicon M251: All versions prior to 5.4.13.12
• Modicon M258: All firmware versions
• Modicon LMC058: All firmware versions

To address the risk, administrators should prioritize the Schneider Electric Modicon M241 firmware update guide procedures provided by the vendor. Firmware version 5.4.13.12, delivered with EcoStruxure Machine Expert v2.5.0.1, includes the necessary patches. This update should be applied using the Schneider Electric Software Installer, followed by a full reboot of the logic controller. This process effectively neutralizes the XSS vector by implementing stricter input validation mechanisms.

Mitigating XSS in Industrial Control Systems

In scenarios where immediate firmware updates are not feasible, particularly for the M258 and LMC058 lines where specific patch versions are not listed, secondary defensive measures are required. Organizations should focus on mitigating XSS in industrial control systems by reducing the available attack surface.

The SOC should verify that all industrial controllers are isolated from the public internet and untrusted business networks. If the integrated webserver is not required for daily operations, it should be deactivated. For environments where remote monitoring is essential, access must be restricted through encrypted VPN tunnels and strictly segmented networks to block unauthorized HTTP/HTTPS traffic on ports 80 and 443.

Defenders seeking how to detect CVE-2025-13902 exploit attempts should monitor SIEM logs for unusual administrative login patterns or suspicious script tags in HTTP POST requests directed at Modicon controllers. Although no known public exploitation has been reported, the presence of a CVE in critical infrastructure components remains a high-priority concern for the Energy and Critical Manufacturing sectors.