CVE-2026-1440 is a reflected Cross-Site Scripting (XSS) vulnerability identified in Graylog Web Interface version 2.2.3. The root cause is the improper neutralization of input during web page generation, specifically the failure to sanitize and escape URL segments before embedding them in HTML responses. The vulnerability manifests in several endpoints, notably '/system/pipelines/', where parts of the URL are directly reflected in the web interface without output encoding. This allows an attacker to craft a specially designed URL containing malicious JavaScript code. When a user accesses this URL, the injected script executes in their browser context. The impact includes execution of arbitrary scripts, which can lead to session token theft, unauthorized actions on behalf of the user, or redirection to malicious sites. The vulnerability does not require any authentication or elevated privileges but does require the victim to interact with the malicious link. 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 known exploits are currently reported, but the flaw represents a moderate risk to affected systems. Graylog is a popular centralized log management platform, and version 2.2.3 is an older release, so organizations running this version should consider upgrading or applying mitigations.

For European organizations, exploitation of this XSS vulnerability could lead to unauthorized script execution in the browsers of users accessing the Graylog Web Interface. This may result in session hijacking, theft of sensitive information, or execution of actions with the victim's privileges within the Graylog console. Although the impact on confidentiality and integrity is rated low, the ability to manipulate user sessions can facilitate further attacks or unauthorized access to log data, which may contain sensitive operational or security information. Given that Graylog is used for log aggregation and monitoring, compromise of its interface could undermine security monitoring capabilities and incident response. The requirement for user interaction (clicking a malicious link) somewhat limits the attack scope, but phishing or social engineering could be used to induce this. European organizations in sectors with high reliance on centralized log management, such as finance, telecommunications, and critical infrastructure, could face operational risks and compliance issues if this vulnerability is exploited.

Organizations should upgrade Graylog to a version where this vulnerability is patched; if no patch is available, consider upgrading to the latest supported release. In the interim, implement strict input validation and output encoding on the web interface endpoints, especially '/system/pipelines/'. Deploy Web Application Firewalls (WAFs) with rules to detect and block reflected XSS attack patterns targeting Graylog URLs. Educate users about phishing risks to reduce the likelihood of clicking malicious links. Restrict access to the Graylog Web Interface to trusted networks or VPNs to minimize exposure. Monitor logs for unusual access patterns or suspicious URLs. Consider implementing Content Security Policy (CSP) headers to limit script execution contexts in browsers accessing Graylog. Regularly review and update security configurations and conduct penetration testing focused on web interface vulnerabilities.