CVE-2025-34278 is a stored cross-site scripting (XSS) vulnerability identified in Nagios Network Analyzer versions prior to 2024R1. The vulnerability resides in the Source Groups page, specifically within the percentile calculator menu, where user-supplied input is improperly sanitized before being stored and later rendered. This improper neutralization of input (CWE-79) allows an attacker with low privileges to inject malicious JavaScript payloads that persist in the application’s data store. When other users access the affected page, the malicious script executes in their browser context, potentially enabling session hijacking, credential theft, or unauthorized actions performed with the victim’s privileges. The CVSS 4.0 vector indicates network attack vector (AV:N), low attack complexity (AC:L), no privileges required (PR:L, meaning low privileges), and user interaction required (UI:P). The vulnerability does not affect confidentiality, integrity, or availability directly but impacts the security integrity of user sessions (SI:L). No patches or known exploits are currently available, but the vulnerability is publicly disclosed and assigned a medium severity score of 5.1. The lack of patch availability necessitates immediate mitigation through access controls and monitoring. The vulnerability’s exploitation requires the attacker to have some level of access to input data fields but does not require administrative privileges, increasing the risk in multi-user environments. Stored XSS vulnerabilities are particularly dangerous because they can affect multiple users and persist over time, unlike reflected XSS which requires immediate interaction. Nagios Network Analyzer is widely used for network traffic analysis and monitoring, making this vulnerability relevant for organizations relying on it for network security and performance insights.

For European organizations, this vulnerability poses a moderate risk primarily to the confidentiality and integrity of user sessions within Nagios Network Analyzer. Successful exploitation could lead to session hijacking, unauthorized command execution within the application context, or theft of sensitive monitoring data. Since Nagios Network Analyzer is often deployed in network operations centers and security monitoring environments, compromised user sessions could allow attackers to manipulate monitoring data or gain footholds for further network intrusion. The impact is heightened in environments with multiple users accessing the Source Groups page, such as large enterprises or managed service providers. Although availability is not directly impacted, trust in monitoring data integrity could be undermined, affecting incident response and network management decisions. The medium CVSS score reflects the balance between ease of exploitation and the limited scope of impact, as exploitation requires user interaction and some privileges. However, given the critical role of network analyzers in infrastructure monitoring, even moderate vulnerabilities warrant prompt attention to prevent lateral movement or escalation in targeted attacks.

Until an official patch is released, European organizations should implement the following specific mitigations: 1) Restrict access to the Source Groups page and percentile calculator menu to only trusted users or administrators via role-based access controls or network segmentation. 2) Employ web application firewalls (WAFs) with robust XSS detection and blocking capabilities to filter malicious payloads targeting the vulnerable input fields. 3) Conduct input validation and sanitization at the proxy or gateway level if possible, to prevent malicious scripts from reaching the application. 4) Monitor application logs and user activity for unusual input patterns or repeated access to the vulnerable page that may indicate exploitation attempts. 5) Educate users about the risks of clicking suspicious links or interacting with untrusted content within the Nagios interface. 6) Prepare for rapid deployment of patches once available by maintaining an up-to-date asset inventory and change management process. 7) Consider temporary disabling or hiding the vulnerable functionality if feasible without disrupting critical operations. These targeted actions go beyond generic advice by focusing on access control, proactive filtering, and monitoring specific to the affected component.