CVE-2026-1437 is a reflected Cross-Site Scripting (XSS) vulnerability classified under CWE-79, discovered in Graylog Web Interface version 2.2.3. The vulnerability stems from the web interface's failure to properly sanitize and encode user-controllable input embedded in HTML responses, specifically URL segments that are reflected without output encoding. This improper neutralization allows attackers to inject arbitrary JavaScript code into the response. The primary affected endpoint is '/system/authentication/users/edit/', where the URL parameters are directly included in the HTML output. When a victim user accesses a specially crafted URL, the malicious script executes in their browser context, enabling potential session manipulation or other client-side attacks. The vulnerability does not require authentication or privileges, but does require user interaction to click or visit the malicious URL. The CVSS 4.0 vector indicates network attack vector (AV:N), low attack complexity (AC:L), no privileges required (PR:N), user interaction required (UI:P), and low impact on confidentiality and integrity (VC:L, VI:L), with no impact on availability. No patches or fixes are currently linked, and no known exploits have been reported in the wild. The vulnerability was published on February 18, 2026, with INCIBE as the assigner. Given the nature of Graylog as a log management and analysis tool often used in enterprise environments, this vulnerability could be leveraged to target administrators or users with access to the Graylog web console.

For European organizations, this vulnerability poses a risk primarily to the confidentiality and integrity of user sessions within the Graylog web interface. Successful exploitation could allow attackers to execute arbitrary scripts in the context of the victim’s browser, potentially stealing session tokens, performing actions on behalf of the user, or conducting phishing attacks. Since Graylog is widely used for centralized log management and security monitoring, compromising its interface could lead to further lateral movement or information disclosure within the organization. The impact is heightened in environments where Graylog is exposed to less trusted networks or where users have elevated privileges. Although the vulnerability does not directly affect availability, the indirect consequences of session hijacking or unauthorized actions could disrupt security operations. European organizations relying on version 2.2.3 should be aware that attackers do not need authentication to exploit this flaw, increasing the attack surface. The lack of known exploits in the wild suggests limited current exploitation, but the medium severity and ease of exploitation warrant proactive mitigation.

Given the absence of an official patch, European organizations should implement immediate compensating controls. First, restrict access to the Graylog web interface to trusted internal networks or VPNs to reduce exposure. Implement web application firewalls (WAFs) with custom rules to detect and block suspicious URL patterns targeting the '/system/authentication/users/edit/' endpoint. Educate users and administrators about the risk of clicking untrusted links, especially those purporting to be related to Graylog. Monitor web server logs for unusual requests containing suspicious scripts or encoded payloads. If possible, upgrade Graylog to a later version where this vulnerability is addressed or apply vendor-provided patches once available. Additionally, consider implementing Content Security Policy (CSP) headers to limit the execution of inline scripts and reduce the impact of XSS attacks. Regularly audit and review user privileges within Graylog to minimize potential damage from compromised sessions.