CVE-2026-9086: Red Hat Build Of Keycloak

High severity, CVSS 7.3. EPSS: 0.8% chance of exploitation in the next 30 days.

A flaw was found in Keycloak. A remote attacker with administrative privileges, specifically those with `manage-client` permission or access to client registration endpoints, could bypass client Uniform Resource Identifier (URI) validation. This is achieved by registering a malicious client with a specially crafted redirect URI using a case-insensitive `javascript:` or `data:` scheme. This Cross-Site Scripting (XSS) vulnerability allows for arbitrary code execution in the Keycloak origin when a victim clicks the crafted link, such as in the logout flow or the Admin Console.

Affected products

• Red Hat Build Of Keycloak: from 26.4, before 26.4.13 (fixed in 26.4.13); from 26.6, before 26.6.4 (fixed in 26.6.4)

Published 2026-06-25. Last modified 2026-07-15.