CVE-2023-7312 is a stored cross-site scripting (XSS) vulnerability classified under CWE-79 affecting Nagios Fusion, a centralized monitoring solution widely used for IT infrastructure management. The vulnerability exists in versions prior to 4.2.0 and is triggered when an attacker with sufficient privileges adds or modifies Email Settings, specifically SMTP or sendmail configuration fields. These fields do not properly sanitize user input, allowing malicious JavaScript code to be stored persistently within the application. When other users with access to the administrative UI view the affected pages, the malicious script executes in their browsers under the context of the Nagios Fusion domain. This can lead to session hijacking, credential theft, or unauthorized actions performed on behalf of the victim user. The attack vector requires network access and authenticated high privileges (e.g., admin or equivalent) to modify email settings, and user interaction is necessary to trigger the payload by viewing the compromised page. The vulnerability has a CVSS 4.0 base score of 6.2, reflecting medium severity due to the need for authentication and user interaction but with potential significant impact on confidentiality and integrity. No public exploits or active exploitation have been reported to date. Mitigation involves upgrading to Nagios Fusion 4.2.0 or later where input sanitization is enforced, or applying manual input validation and restricting access to email configuration interfaces.

For European organizations, this vulnerability poses a risk primarily to the confidentiality and integrity of administrative sessions and data within Nagios Fusion environments. Successful exploitation could allow attackers to execute arbitrary JavaScript in the context of administrative users, potentially leading to credential theft, session hijacking, or unauthorized configuration changes. This could disrupt monitoring operations, delay incident response, and expose sensitive infrastructure information. Organizations relying heavily on Nagios Fusion for critical infrastructure monitoring, especially in sectors like finance, energy, telecommunications, and government, could face operational risks and compliance issues under GDPR if personal or sensitive data is compromised. Although exploitation requires authenticated access, insider threats or compromised credentials could facilitate attacks. The absence of known exploits reduces immediate risk but does not eliminate the threat, making proactive remediation essential.

1. Upgrade Nagios Fusion to version 4.2.0 or later, where the vulnerability is patched with proper input sanitization. 2. Restrict access to the Email Settings configuration interface strictly to trusted administrators to minimize the risk of malicious input. 3. Implement multi-factor authentication (MFA) for all administrative accounts to reduce the risk of credential compromise. 4. Conduct regular audits of SMTP/email configuration changes to detect unauthorized modifications. 5. Employ web application firewalls (WAFs) with rules to detect and block common XSS payloads targeting Nagios Fusion interfaces. 6. Educate administrators on the risks of stored XSS and encourage cautious handling of configuration inputs. 7. Monitor logs and user activity for unusual behavior indicative of attempted exploitation. 8. If immediate upgrade is not feasible, consider applying input validation proxies or filters to sanitize email configuration inputs.