CVE-2021-47689: 
Nagios XI vulnerability analysis and mitigation

The Core Config Manager (CCM) in Nagios XI versions prior to CCM 3.1.0 / Nagios XI 5.8.0 contains a cross-site scripting (XSS) vulnerability in the Templates pages, specifically in the UI logic that renders and handles the Active/Actions buttons. The vulnerability was discovered and reported by Matthew Aberegg and was disclosed on October 30, 2025 (VulnCheck Advisory).

The vulnerability is classified as CWE-79 (Improper Neutralization of Input During Web Page Generation) with a CVSS v4.0 base score of 5.1 (Medium). The attack vector is network-based (AV:N) with low attack complexity (AC:L), requiring low privileges (PR:L) and passive user interaction (UI:P). The vulnerability has no direct impact on confidentiality, integrity, or availability (VC:N/VI:N/VA:N) but has low subsequent impact on confidentiality and integrity (SC:L/SI:L) (VulnCheck Advisory).

The vulnerability allows an attacker to inject and execute arbitrary script in the context of a victim's browser due to insufficient validation or escaping of user-supplied input (VulnCheck Advisory).

Users should upgrade to Nagios XI version 5.8.0 or CCM version 3.1.0 or later to address this vulnerability (Nagios Changelog).