CVE-2018-25121 in Nagios
Summary
by MITRE • 10/31/2025
Nagios XI versions prior to 5.4.13 are vulnerable to cross-site scripting (XSS) via the Views page of the web interface. Insufficient validation or escaping of user-supplied input may allow an attacker to inject and execute arbitrary script in the context of a victim's browser.
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Analysis
by VulDB Data Team • 11/17/2025
Nagios XI is a comprehensive network monitoring and management platform that provides real-time visibility into network infrastructure health and performance. The platform's web interface serves as the primary administrative portal for system administrators to configure monitoring settings, view alerts, and manage various network components. The vulnerability exists within the Views page functionality, which allows users to create and customize dashboard views for monitoring network data. This page accepts user-supplied input for various configuration parameters including view names, filter criteria, and display settings. The insufficient input validation and output escaping mechanisms fail to properly sanitize user-provided data before rendering it within the web interface context, creating a persistent cross-site scripting vulnerability that can be exploited by malicious actors.
The technical flaw in CVE-2018-25121 stems from inadequate sanitization of user input within the Views page functionality of Nagios XI. When administrators or users create or modify views, the system processes parameters such as view titles, filter expressions, and custom display configurations without proper HTML escaping or input validation. This vulnerability specifically manifests when user-supplied data containing malicious script code is processed by the web application and subsequently rendered in the browser context without adequate security controls. The flaw aligns with CWE-79 which defines cross-site scripting as the improper validation of input or insufficient escaping of output, and represents a classic reflected XSS vulnerability pattern. Attackers can craft malicious payloads that when executed in a victim's browser session can perform unauthorized actions, steal session cookies, or redirect users to malicious sites.
The operational impact of this vulnerability extends beyond simple script execution as it can compromise the integrity of the entire monitoring infrastructure. An attacker who successfully exploits this vulnerability gains the ability to execute arbitrary JavaScript code within the context of any authenticated user's browser session. This means that if a system administrator with elevated privileges accesses the compromised Views page, the attacker could potentially hijack administrative sessions, modify monitoring configurations, or exfiltrate sensitive network data. The vulnerability affects all versions prior to 5.4.13, making it particularly concerning for organizations that maintain older installations. The attack vector requires user interaction through the web interface, typically involving social engineering to trick administrators into visiting malicious URLs or clicking on compromised links that contain the malicious script payloads.
Organizations should immediately implement the remediation measures provided by Nagios, including upgrading to version 5.4.13 or later which contains the necessary input validation and output escaping fixes. Network administrators should also consider implementing additional security controls such as web application firewalls to detect and block malicious script injection attempts. The vulnerability demonstrates the critical importance of proper input validation and output escaping in web applications, particularly in management interfaces that handle sensitive operational data. Security teams should conduct comprehensive vulnerability assessments of their Nagios XI installations to identify any other potential XSS vulnerabilities in related components. The incident highlights the necessity of maintaining current software versions and implementing defense-in-depth strategies that include regular security updates, access controls, and monitoring for suspicious activities within the monitoring infrastructure. This vulnerability also aligns with ATT&CK technique T1059 which covers execution through scripting and command-line interfaces, emphasizing the need for comprehensive application security controls in monitoring and management platforms.