CVE-2020-36866 in Nagios
Summary
by MITRE • 10/31/2025
Nagios XI versions prior to 5.7.3 are vulnerable to cross-site scripting (XSS) via the Manage Users page of the Admin 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 • 11/08/2025
Nagios XI is a comprehensive network monitoring and management platform that provides administrators with centralized visibility into system performance, availability, and security posture across enterprise environments. The platform's administrative interface serves as a critical control point where users can manage system configurations, user accounts, and monitoring parameters. This particular vulnerability exists within the Manage Users page of the administrative interface, which represents a high-value target for attackers seeking to compromise the monitoring infrastructure. The affected versions prior to 5.7.3 demonstrate a classic security flaw that undermines the integrity of the administrative controls and potentially exposes the entire monitoring ecosystem to unauthorized access and manipulation.
The technical flaw manifests as a cross-site scripting vulnerability that occurs when the application fails to properly validate or escape user-supplied input submitted through the Manage Users interface. When administrators or authenticated users navigate to the Manage Users page and interact with input fields, the application processes the data without adequate sanitization measures. This insufficient input validation creates an opportunity for malicious actors to inject malicious scripts into the application's response, which then executes within the browser context of legitimate users who view the affected page. The vulnerability specifically affects the administrative interface, meaning that successful exploitation could enable attackers to perform actions with the privileges of the authenticated user, potentially escalating to full administrative control over the monitoring platform.
The operational impact of this vulnerability extends beyond simple script execution, as it represents a significant threat to the integrity and confidentiality of the monitoring environment. An attacker who successfully exploits this XSS vulnerability could potentially access sensitive monitoring data, manipulate user accounts, or even execute commands with elevated privileges within the Nagios XI environment. The administrative interface serves as a critical control point for network monitoring, making this vulnerability particularly dangerous as it could allow attackers to disable monitoring alerts, modify system configurations, or gain unauthorized access to the underlying network infrastructure that Nagios XI is designed to monitor. The vulnerability's presence in the user management functionality means that attackers could potentially create or modify administrator accounts, effectively taking complete control of the monitoring platform.
Mitigation strategies for this vulnerability should focus on immediate patching of affected Nagios XI installations to version 5.7.3 or later, which contains the necessary input validation and output escaping mechanisms to prevent XSS injection. Organizations should also implement additional security measures including regular security assessments of the monitoring platform, network segmentation to limit access to the administrative interface, and monitoring of suspicious activities within the administrative controls. The vulnerability aligns with CWE-79 which specifically addresses cross-site scripting flaws in web applications, and represents a typical example of how insufficient input validation can lead to severe security consequences. From an ATT&CK framework perspective, this vulnerability maps to techniques involving initial access through web application attacks and privilege escalation through administrative interface compromise, making it a critical target for both defensive and offensive security operations.