CVE-2026-42401 Elastic CVE debrief

Who should care

Organizations running Kibana with multi-user Elasticsearch environments where index-level access controls are shared among users with varying trust levels. Security teams monitoring for stored injection attacks in data visualization platforms. Compliance teams tracking XSS vulnerabilities in analytics infrastructure.

Technical summary

The vulnerability exists in Kibana's rendering of content from Elasticsearch indices. A user with index write permissions can store crafted HTML markup that Kibana subsequently renders without sufficient sanitization. The CVSS 3.1 score of 4.1 (Medium) reflects the required user interaction and limited scope of impact. Successful exploitation requires: (1) attacker with write access to an Elasticsearch index, (2) victim with access to view the affected Kibana visualization or dashboard, and (3) victim interaction with the rendered content. The attack can result in UI defacement, session manipulation, or triggering unauthorized outbound requests from the victim's browser.

Defensive priority

medium

Recommended defensive actions

• Upgrade Kibana to version 8.19.1, 6.9.3-5, or later as specified in the Elastic security advisory
• Review Elasticsearch index permissions to restrict write access to trusted users only
• Implement Content Security Policy headers to mitigate impact of HTML injection
• Monitor Kibana access logs for unusual outbound network request patterns
• Audit existing Elasticsearch indices for potentially malicious stored markup

Evidence notes

The vulnerability description and affected product identification are sourced from the official Elastic security advisory and NVD record. The CVSS 3.1 vector (AV:N/AC:L/PR:L/UI:R/S:C/C:N/I:L/A:N) indicates network attack vector with low attack complexity, requiring low privileges and user interaction, with scope change and low integrity impact.

Official resources