CVE-2017-20209 in Fusion
Summary
by MITRE • 10/31/2025
Nagios Fusion versions prior to 4.0.1 are vulnerable to cross-site scripting (XSS) via the Users and Servers pages. 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 Fusion represents a comprehensive network monitoring solution that provides centralized management and visualization of network infrastructure components. The vulnerability identified as CVE-2017-20209 affects versions prior to 4.0.1, specifically targeting the Users and Servers pages within the application interface. This exposure creates a significant security risk as these pages serve as critical access points for administrators to manage system configurations and monitor network status. The affected components within Nagios Fusion typically handle user authentication data, server configuration parameters, and monitoring metrics that require robust input validation to prevent unauthorized code execution.
The technical flaw manifests through inadequate input sanitization mechanisms that fail to properly validate or escape user-supplied data before rendering it within the web interface. When users interact with the Users and Servers pages, any malicious input containing script code is not adequately filtered or escaped, allowing attackers to inject malicious javascript payloads. This vulnerability specifically relates to CWE-79 which defines Cross-Site Scripting as the failure to properly escape output data, enabling attackers to execute scripts in the victim's browser context. The flaw occurs at the application layer where user input is directly incorporated into dynamic web content without proper security controls.
The operational impact of this vulnerability extends beyond simple data theft or service disruption. An attacker exploiting this XSS flaw can potentially hijack user sessions, redirect victims to malicious websites, or execute commands with the privileges of authenticated users. Given that Nagios Fusion is commonly deployed in enterprise environments where it serves as a central monitoring hub, successful exploitation could provide attackers with access to critical network information and potentially facilitate further lateral movement within the infrastructure. The vulnerability affects both administrative and regular user accounts, making it particularly dangerous as it could compromise the entire monitoring ecosystem.
Mitigation strategies should prioritize immediate patch deployment to upgrade to Nagios Fusion version 4.0.1 or later, which includes proper input validation and output escaping mechanisms. Organizations should also implement additional security controls such as web application firewalls that can detect and block malicious script injection attempts. Network segmentation and privileged access controls can help limit the potential impact if exploitation occurs. Security teams should conduct regular vulnerability assessments and penetration testing to identify similar issues in other monitoring tools and web applications. The remediation process should include thorough testing of the patched version to ensure that the XSS protections do not introduce compatibility issues with existing monitoring configurations and user workflows. This vulnerability exemplifies the importance of maintaining up-to-date security patches and implementing comprehensive input validation as recommended by the ATT&CK framework's defense evasion techniques.