CVE-2025-5514 is a medium-severity vulnerability affecting the Mitsubishi Electric Corporation MELSEC iQ-F Series FX5U-32MT/ES CPU module, specifically its embedded web server function. The root cause is an improper handling of length parameter inconsistency (CWE-130) within the web server's processing logic. This flaw allows a remote, unauthenticated attacker to send specially crafted HTTP requests that exploit the length parameter inconsistency, causing the web server to delay processing. This results in a denial-of-service (DoS) condition where legitimate users are prevented from accessing or utilizing the web server function. The vulnerability does not impact confidentiality or integrity but affects availability by slowing or halting web server responses. The CVSS 3.1 base score is 5.3, reflecting a medium severity with network attack vector, no privileges or user interaction required, and limited impact to availability only. The affected product versions are 1.060 and later. No known exploits are currently reported in the wild, and no patches have been linked yet. Given the MELSEC iQ-F Series FX5U-32MT/ES is an industrial control system (ICS) component widely used in automation and manufacturing environments, this vulnerability could disrupt operational technology (OT) environments relying on web server access for monitoring or control. Attackers could leverage this flaw to degrade system availability remotely without authentication, potentially impacting industrial processes or safety systems that depend on timely web server responses.

For European organizations, especially those in manufacturing, utilities, and critical infrastructure sectors that deploy Mitsubishi Electric MELSEC iQ-F Series controllers, this vulnerability poses a risk of operational disruption. The denial-of-service condition could delay or block access to web-based management interfaces, hindering monitoring, diagnostics, and control activities. This could lead to production downtime, delayed response to system faults, or impaired safety monitoring. While the vulnerability does not allow data theft or system takeover, the availability impact in industrial environments can have significant financial and safety consequences. European industries with automated manufacturing lines or infrastructure control systems using these PLCs may experience interruptions, potentially affecting supply chains and service delivery. The lack of authentication requirement and network-based exploitability increases the risk of opportunistic attacks from external threat actors or insiders with network access. However, the absence of known exploits in the wild and the medium severity rating suggest the threat is moderate but warrants timely mitigation to avoid escalation.

Organizations should immediately inventory their industrial control systems to identify deployments of the MELSEC iQ-F Series FX5U-32MT/ES CPU modules running firmware version 1.060 or later. Until an official patch is released by Mitsubishi Electric, the following specific mitigations are recommended: 1) Restrict network access to the web server interface by implementing network segmentation and firewall rules to limit exposure only to trusted management networks and personnel. 2) Employ intrusion detection/prevention systems (IDS/IPS) tuned to detect anomalous HTTP requests or unusual traffic patterns targeting the PLC web server. 3) Monitor network traffic for repeated or malformed HTTP requests that could indicate exploitation attempts. 4) Disable or restrict the web server function if it is not essential for operations, or replace web-based management with alternative secure methods. 5) Coordinate with Mitsubishi Electric for firmware updates and apply patches promptly once available. 6) Conduct regular security assessments of OT networks to identify and remediate similar protocol handling vulnerabilities. These targeted mitigations go beyond generic advice by focusing on access control, traffic monitoring, and operational adjustments specific to the affected ICS components.