CVE-2025-41707 identifies a classic buffer overflow vulnerability (CWE-120) in the websocket handler component of the Phoenix Contact QUINT4-UPS/24DC/24DC/5/EIP uninterruptible power supply (UPS) device. The flaw arises because the device fails to properly check the size of input data when processing websocket messages, allowing an attacker to overflow a buffer. This can be exploited remotely without authentication by sending a specially crafted websocket message, leading to a denial of service condition where the device's websocket handler crashes or becomes unresponsive. Importantly, the core functionality of the UPS remains unaffected, indicating the device continues to provide power backup but loses websocket communication capabilities. The vulnerability has a CVSS 3.1 base score of 5.3, reflecting medium severity with network attack vector, low attack complexity, no privileges required, and no user interaction needed. No patches or fixes have been released as of the publication date, and no active exploitation has been reported. The affected product is a specialized industrial UPS device commonly deployed in automation and critical infrastructure environments. The vulnerability could be leveraged to disrupt monitoring or management systems relying on websocket communication with the UPS, potentially delaying response to power events or maintenance needs.

For European organizations, especially those operating industrial automation, manufacturing plants, or critical infrastructure such as energy and utilities, this vulnerability poses a risk of denial of service on the management interface of Phoenix Contact QUINT4-UPS devices. While the UPS's primary power backup function remains intact, loss of websocket communication can hinder remote monitoring, diagnostics, and automated management, increasing operational risk and response times during power incidents. This could lead to prolonged downtime or delayed mitigation of power-related issues. Organizations relying on centralized monitoring platforms that use websocket connections to these UPS devices may experience partial visibility loss. The medium severity and lack of core functionality impact reduce the likelihood of catastrophic failure but still represent a significant operational disruption vector. The vulnerability's unauthenticated remote exploitability increases risk, especially in environments where these devices are exposed to less secure network segments or the internet.

Since no patches are currently available, European organizations should implement compensating controls to mitigate risk. These include: 1) Restricting network access to the websocket interface of affected UPS devices using firewalls, VLAN segmentation, or access control lists to limit exposure to trusted management networks only. 2) Monitoring websocket traffic for anomalous or malformed messages that could indicate exploitation attempts. 3) Employing intrusion detection/prevention systems (IDS/IPS) with signatures or heuristics targeting websocket buffer overflow patterns. 4) Isolating critical UPS devices from direct internet exposure and enforcing strict network segmentation between operational technology (OT) and IT networks. 5) Engaging with Phoenix Contact support for updates or firmware patches and planning timely deployment once available. 6) Reviewing and hardening device configurations to disable unnecessary services or interfaces if possible. 7) Conducting regular security audits and penetration tests focusing on industrial control system components to identify similar vulnerabilities.