CVE-2025-40893 is a stored HTML injection vulnerability classified under CWE-79 (Improper Neutralization of Input During Web Page Generation) affecting Nozomi Networks Guardian, a cybersecurity product used primarily for operational technology (OT) and industrial control system (ICS) security. The vulnerability arises from improper validation of network traffic data within the Asset List functionality. Specifically, an unauthenticated attacker can send specially crafted network packets that include malicious HTML tags embedded within asset attributes. These injected tags are stored and later rendered in the web interface when a user views the affected assets. This stored injection enables phishing attacks by displaying deceptive content and may facilitate open redirect attacks, potentially redirecting users to malicious sites. However, the product's existing input validation and Content Security Policy (CSP) configurations prevent full cross-site scripting (XSS) exploitation and direct information disclosure, limiting the attack's scope. The vulnerability does not require authentication, increasing its risk profile, but does require user interaction to trigger the malicious payload. The CVSS 4.0 base score of 5.3 reflects a medium severity, considering the network attack vector, low complexity, no privileges required, but user interaction needed and limited impact on confidentiality and availability. No patches are listed yet, and no known exploits are reported in the wild as of the publication date.

For European organizations, especially those operating critical infrastructure and industrial environments where Nozomi Networks Guardian is deployed, this vulnerability poses a risk of social engineering attacks such as phishing and redirection to malicious websites. Such attacks could lead to credential theft, session hijacking, or further exploitation of network resources. Although direct data leakage or system compromise is mitigated, the ability to inject HTML content undermines user trust and could facilitate lateral attacks within OT environments. The unauthenticated nature of the attack increases exposure, particularly in environments where network traffic is not tightly controlled or segmented. Disruption to operational technology monitoring or response activities could have downstream effects on industrial processes, safety, and compliance with European cybersecurity regulations such as NIS2. The medium severity suggests a moderate risk, but the critical nature of affected sectors elevates the importance of timely mitigation.

1. Apply vendor patches immediately once available to address the input validation flaw in the Asset List functionality. 2. Implement strict network segmentation and filtering to limit exposure of Nozomi Guardian interfaces to untrusted networks, reducing the attack surface for unauthenticated packet injection. 3. Enhance monitoring and alerting for anomalous network traffic patterns that could indicate attempts to inject malicious payloads. 4. Review and tighten Content Security Policy configurations to further restrict the execution of injected HTML or scripts. 5. Educate users on recognizing phishing attempts and suspicious redirects within the Guardian interface. 6. Conduct regular security assessments and penetration testing focused on web interface vulnerabilities in OT security products. 7. Consider deploying Web Application Firewalls (WAFs) or Intrusion Prevention Systems (IPS) capable of detecting and blocking malicious HTML injection attempts targeting the Guardian platform. 8. Maintain up-to-date asset inventories and ensure that all Guardian deployments are tracked and managed centrally to facilitate rapid response.