CVE-2025-40890 is a stored Cross-Site Scripting (XSS) vulnerability identified in the Dashboards feature of Nozomi Networks Guardian, a cybersecurity solution commonly deployed for operational technology (OT) and industrial control system (ICS) monitoring. The vulnerability stems from improper neutralization of input during web page generation, specifically a failure to adequately validate or sanitize user-supplied input parameters used in dashboard creation. An attacker with low-privilege authenticated access can craft a malicious dashboard embedding JavaScript payloads. This malicious dashboard can then be shared with other users or distributed as a dashboard template that victims may import. When a victim views or imports the compromised dashboard, the embedded script executes within their browser context, inheriting their session privileges. This enables the attacker to perform unauthorized actions including modifying application data, disrupting the availability of the application, and accessing sensitive information that should be restricted. The attack requires the attacker to have some level of authenticated access and relies on user interaction (viewing or importing the dashboard). The CVSS 4.0 vector indicates network attack vector (AV:N), high attack complexity (AC:H), no privileges required (PR:L), user interaction required (UI:A), and impacts on confidentiality, integrity, and availability at high or low levels depending on the component. The vulnerability is classified under CWE-79, which covers improper neutralization of input leading to XSS. No public exploits have been reported yet, but the potential for abuse exists in environments where dashboards are shared among users. The affected version is listed as '0', which likely indicates all versions prior to a patch or a placeholder. The vulnerability was published on November 25, 2025. Given the nature of Nozomi Guardian's deployment in critical infrastructure and industrial environments, this vulnerability poses a risk to operational security and data integrity.

For European organizations, especially those operating critical infrastructure, manufacturing, energy, and industrial sectors, this vulnerability can have significant consequences. Nozomi Networks Guardian is widely used for OT and ICS security monitoring, meaning that exploitation could lead to unauthorized modification of monitoring data, potentially masking malicious activities or causing incorrect operational decisions. The ability to disrupt application availability could impair security monitoring capabilities, increasing the risk of undetected attacks. Access to sensitive information could expose operational details or credentials, further compromising security. Since the attack requires authenticated access and user interaction, insider threats or compromised low-privilege accounts pose a notable risk. The medium CVSS score reflects a moderate but meaningful threat level, especially in environments where dashboards are shared extensively or where users may be socially engineered to import malicious templates. The impact on confidentiality, integrity, and availability in critical OT environments could cascade into physical process disruptions or safety incidents, amplifying the threat beyond typical IT systems.

To mitigate CVE-2025-40890 effectively, European organizations should implement the following specific measures: 1) Restrict dashboard creation and sharing permissions to trusted users only, minimizing the number of low-privilege users who can create or share dashboards. 2) Enforce strict input validation and sanitization on all user-supplied data used in dashboard generation, ideally through vendor patches or custom web application firewalls (WAFs) that detect and block malicious scripts. 3) Educate users about the risks of importing dashboards from untrusted sources and implement policies to verify dashboard templates before import. 4) Monitor dashboard usage and sharing activities for anomalous behavior indicative of malicious payload distribution. 5) Apply vendor patches promptly once available, and engage with Nozomi Networks for updates or workarounds. 6) Consider network segmentation and access controls to limit exposure of the Guardian dashboard interface to only necessary personnel. 7) Implement browser security controls such as Content Security Policy (CSP) headers to reduce the impact of XSS payloads. These targeted actions go beyond generic advice by focusing on the unique operational context of Nozomi Guardian deployments and the specific attack vectors involved.