CVE-2026-9086

Keycloak: keycloak: cross-site scripting (xss) via case-insensitive uri validation bypass

Published Jun 25, 2026 CVSS 3.1 · 7.3 High EPSS < 1% KEV · Not listed
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.

Remediation

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.

Tracking

Sign in to view the affected projects.

Advisories

Source ID Title
Github GHSA Github GHSA GHSA-v3f7-2p4r-mwfw Keycloak vulnerable to cross-site scripting (xss) via case-insensitive uri validation bypass
History
Type Values Removed Values Added
First Time appeared Redhat build Of Keycloak
Vendors & Products Redhat build Of Keycloak
Type Values Removed Values Added
CPEs cpe:/a:redhat:build_keycloak: cpe:/a:redhat:build_keycloak:26.6::el9
References
Type Values Removed Values Added
Metrics ssvc

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

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'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
redhat
Published
Updated
Jul 15, 2026, 12:38 AM
Reserved
May 20, 2026, 2:44 PM
Status
Analyzed
Published
Jun 25, 2026, 5:17 PM
Modified
Jul 15, 2026, 1:17 AM
Severity
Important
Public date
Jun 25, 2026, 3:58 PM