CVE-2026-9086
Keycloak: keycloak: cross-site scripting (xss) via case-insensitive uri validation bypass
- Published
- Jun 25, 2026
- Updated
- Jul 15, 2026
- Assigning CNA
- redhat
- Evidence observed
- Aug 10, 2026
Primary CVSS
nvd · CVSS 3.1
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:NLow · next 30 days
- Percentile
- 54.0%
- Model date
- Sep 21, 2026
EPSS is a statistical estimate, not a certainty or a measure of impact. Combine it with CVSS, KEV status, exposure and your environment.
Summary
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.
Sources
1CVE-2026-9086 proof-of-concept for Keycloak client URI validation bypass using mixed-case javascript: and data: XSS payloads, with Docker-based verification of vulnerable and fixed versions.
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