CVE-2022-3561 is a Cross-site Scripting (XSS) vulnerability identified in the LibreNMS network monitoring software prior to version 22.10.0. The vulnerability is classified under CWE-79, which involves improper neutralization of input during web page generation. This type of vulnerability allows an attacker to inject malicious scripts into web pages viewed by other users. Specifically, the flaw arises because user-supplied input is not adequately sanitized or escaped before being included in dynamically generated web content. When exploited, this can lead to the execution of arbitrary JavaScript in the context of the victim's browser session. The CVSS v3.0 base score is 4.3 (medium severity), with vector AV:N/AC:L/PR:H/UI:R/S:U/C:L/I:L/A:L, indicating that the attack can be performed remotely over the network, requires low attack complexity, but does require high privileges and user interaction. The impact includes limited confidentiality, integrity, and availability consequences, as the attacker can potentially steal session cookies, perform actions on behalf of the user, or cause minor disruptions. No known exploits are currently reported in the wild, and no official patches or mitigation links were provided in the source information. LibreNMS is an open-source network monitoring tool widely used by IT teams to monitor infrastructure health and performance, making this vulnerability relevant to organizations relying on it for network visibility and management.

For European organizations using LibreNMS, this XSS vulnerability poses a moderate risk primarily to the confidentiality and integrity of user sessions within the monitoring platform. An attacker exploiting this flaw could execute malicious scripts in the context of authenticated users, potentially leading to session hijacking, unauthorized actions within the monitoring interface, or phishing attacks targeting network administrators. While the vulnerability does not directly compromise network devices, the indirect effects could include manipulation or disruption of monitoring data, delayed detection of network issues, or exposure of sensitive network topology information. Given that LibreNMS is often deployed in critical infrastructure environments, including telecommunications, finance, and government sectors across Europe, exploitation could degrade operational security and trust in network monitoring. The requirement for high privileges and user interaction reduces the likelihood of widespread automated exploitation but does not eliminate targeted attacks against privileged users. The absence of known exploits in the wild suggests limited active exploitation currently, but organizations should remain vigilant due to the sensitive nature of the monitored data and the strategic importance of network monitoring platforms.

To mitigate this vulnerability, European organizations should prioritize upgrading LibreNMS to version 22.10.0 or later, where the issue is resolved. In the absence of an official patch, administrators should implement strict input validation and output encoding on all user-supplied data within the LibreNMS interface, focusing on areas where user input is reflected in web pages. Deploying Web Application Firewalls (WAFs) with custom rules to detect and block typical XSS payloads targeting LibreNMS can provide an additional protective layer. Restricting access to the LibreNMS web interface to trusted networks and enforcing strong multi-factor authentication (MFA) for all users with elevated privileges will reduce the risk of exploitation. Regularly auditing user accounts and monitoring logs for suspicious activities related to web interface interactions can help detect attempted attacks early. Additionally, educating network administrators about the risks of clicking on untrusted links or executing scripts within the LibreNMS context can minimize successful social engineering attempts that require user interaction.