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.

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Advisories

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Fixes

Solution

No solution given by the vendor.


Workaround

To mitigate this vulnerability, restrict the ability to register new clients and manage existing client configurations. If Dynamic Client Registration is not required, disable it in Keycloak's Realm Settings under Client Registration Policies. If Dynamic Client Registration is necessary, ensure that policies are strictly configured to prevent anonymous client registration and require initial access tokens for all client registrations. Additionally, limit the `manage-client` role to only trusted administrators. Changes to Keycloak configuration may require a service restart or redeployment to take effect.

History

Thu, 25 Jun 2026 20:00:00 +0000

Type Values Removed Values Added
CPEs cpe:/a:redhat:build_keycloak: cpe:/a:redhat:build_keycloak:26.6::el9
References

Thu, 25 Jun 2026 18:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}


Thu, 25 Jun 2026 16:45:00 +0000

Type Values Removed Values Added
Description 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.
Title Keycloak: keycloak: cross-site scripting (xss) via case-insensitive uri validation bypass
First Time appeared Redhat
Redhat build Keycloak
Weaknesses CWE-79
CPEs cpe:/a:redhat:build_keycloak:
Vendors & Products Redhat
Redhat build Keycloak
References
Metrics cvssV3_1

{'score': 7.3, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:N'}


Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: redhat

Published:

Updated: 2026-06-25T18:54:59.702Z

Reserved: 2026-05-20T14:44:12.702Z

Link: CVE-2026-9086

cve-icon Vulnrichment

Updated: 2026-06-25T17:59:52.871Z

cve-icon NVD

No data.

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-06-25T18:45:03Z

Weaknesses