CVE-2024-11390 is a medium-severity vulnerability affecting Elastic Kibana versions 7.17.6 and 8.4.0, categorized under CWE-434 (Unrestricted Upload of File with Dangerous Type). The vulnerability arises from Kibana's Synthetics app or synthetics indices allowing an attacker with write access to upload files without proper restrictions on file types. Specifically, an attacker can upload crafted HTML or JavaScript files that, when accessed by a victim, execute arbitrary JavaScript code in the victim's browser, resulting in a cross-site scripting (XSS) attack. This can lead to unauthorized actions performed in the context of the victim's session, data theft, or further compromise of the Kibana environment. Exploitation requires the attacker to have either access to the Synthetics app or write permissions to the synthetics indices, which implies some level of authenticated access or insider threat. The vulnerability does not require user interaction beyond the victim accessing the malicious file, and the scope is limited to users who interact with the uploaded content. The CVSS 3.1 base score is 5.4 (medium), reflecting network attack vector, low attack complexity, required privileges, and user interaction. No known exploits are reported in the wild as of the publication date. No official patches have been linked yet, so mitigation relies on access control and monitoring. The vulnerability impacts confidentiality and integrity by enabling arbitrary script execution but does not affect availability directly.

For European organizations using Elastic Kibana, particularly versions 7.17.6 and 8.4.0, this vulnerability poses a risk of session hijacking, data leakage, and unauthorized actions within Kibana dashboards and monitoring tools. Since Kibana is widely used for data visualization and monitoring in enterprise environments, exploitation could lead to exposure of sensitive operational data and potential manipulation of monitoring outputs. The requirement for write access to synthetics indices or access to the Synthetics app limits the attack surface but does not eliminate risk, especially in environments with multiple users or insufficient access controls. European organizations in sectors such as finance, telecommunications, and critical infrastructure, which rely heavily on Kibana for real-time analytics, could face targeted attacks aiming to disrupt monitoring or exfiltrate data. The vulnerability could also be leveraged as a foothold for lateral movement within networks. Given the medium severity and the absence of known exploits, the immediate risk is moderate but warrants prompt attention to prevent escalation.

1. Restrict access to the Kibana Synthetics app and synthetics indices strictly on a need-to-use basis, employing role-based access controls (RBAC) to minimize the number of users with write permissions. 2. Implement strict input validation and file type restrictions at the application or proxy level to block uploads of HTML, JavaScript, or other executable file types until an official patch is available. 3. Monitor Kibana logs and audit trails for unusual file upload activities or access patterns related to the Synthetics app. 4. Educate users with access about the risks of uploading untrusted files and enforce policies to prevent misuse. 5. Deploy Content Security Policy (CSP) headers in Kibana to mitigate the impact of potential XSS by restricting script execution sources. 6. Regularly update Kibana to the latest versions once patches addressing this vulnerability are released by Elastic. 7. Consider network segmentation to isolate Kibana instances from less trusted networks and users. 8. Use Web Application Firewalls (WAF) with custom rules to detect and block suspicious file uploads or script execution attempts related to this vulnerability.