CVE-2021-37936 is a medium-severity vulnerability affecting Elastic Kibana versions prior to 7.14.1. The root cause is improper neutralization of input during web page generation, specifically related to the handling of document fields containing HTML snippets. Kibana, a data visualization and exploration tool for Elasticsearch, failed to sanitize HTML content embedded within documents indexed in Elasticsearch. An attacker with privileges to write documents into an Elasticsearch index can inject malicious HTML code. When a user utilizes the Discover app in Kibana and searches for terms that match the injected HTML content, the application renders this HTML in the search results, leading to a cross-site scripting (XSS) condition (CWE-79). This vulnerability requires the attacker to have low privileges (write access to the Elasticsearch index) and user interaction (the victim must perform a search that triggers rendering of the malicious HTML). The vulnerability impacts confidentiality and integrity by potentially allowing execution of arbitrary scripts in the context of the victim's browser session, which could lead to session hijacking, credential theft, or unauthorized actions within Kibana. Availability is not impacted. The vulnerability has a CVSS 3.1 base score of 5.4, reflecting network attack vector, low attack complexity, required privileges, and user interaction. No known exploits in the wild have been reported. The issue was addressed in Kibana version 7.14.1 by properly sanitizing HTML content in document fields before rendering in the Discover app.

For European organizations using Elastic Kibana versions prior to 7.14.1, this vulnerability poses a risk of cross-site scripting attacks that can compromise user sessions and data integrity within Kibana dashboards. Given Kibana's widespread use in enterprise environments for monitoring and analyzing critical infrastructure and business data, exploitation could lead to unauthorized access to sensitive information, manipulation of displayed data, or execution of malicious scripts that could pivot to further internal systems. The requirement for write access to Elasticsearch indexes limits the attack surface to insiders or compromised accounts with such privileges. However, once exploited, the vulnerability could undermine trust in data visualization and monitoring tools, potentially impacting operational decision-making. The lack of known exploits reduces immediate risk, but the medium severity and ease of exploitation warrant prompt remediation. Organizations in sectors with strict data protection regulations, such as finance, healthcare, and critical infrastructure, may face compliance and reputational risks if this vulnerability is exploited.

1. Upgrade Kibana to version 7.14.1 or later, where this vulnerability is patched. 2. Restrict write permissions to Elasticsearch indexes strictly to trusted users and service accounts, employing the principle of least privilege. 3. Implement robust access controls and monitoring on Elasticsearch clusters to detect unauthorized document writes. 4. Use Content Security Policy (CSP) headers in Kibana deployments to limit the impact of potential XSS attacks by restricting script execution sources. 5. Educate users to avoid executing searches with untrusted input and monitor for unusual search patterns that could indicate exploitation attempts. 6. Regularly audit Kibana and Elasticsearch logs for anomalous activities related to document creation or modification. 7. Consider deploying web application firewalls (WAFs) with rules tailored to detect and block malicious HTML or script injections targeting Kibana interfaces.