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Review reviewHigh

CVE-2026-9086

Red Hat Red Hat build of Keycloak 26.4, Red Hat build of Keycloak 26.4.13, Red Hat build of Keycloak 26.6

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.

CVSS
7.3
EPSS
0.42%
34.0% percentile
CISA KEV
Not listed
Published
2026.06.26
PRIORITY ASSESSMENT

Review review

The CVSS severity warrants an early asset and exposure review.

Known exploitationNot established by KEV
Exploit probability0.42%
Technical severityCVSS 7.3

Vulnerability overview

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 product and versions

Product
Red Hat Red Hat build of Keycloak 26.4, Red Hat build of Keycloak 26.4.13, Red Hat build of Keycloak 26.6
Affected versions
>= 26.4 < 26.4.13, >= 26.6 < 26.6.4
Fixed versions
26.4.13, 26.6.4

Recommended response sequence

Confirm exposure before applying a vendor-supported change.

Full remediation guide
  1. 1
    Identify

    Confirm that Red Hat Red Hat build of Keycloak 26.4, Red Hat build of Keycloak 26.4.13, Red Hat build of Keycloak 26.6 and an affected version are present.

  2. 2
    Prioritize

    Combine exploitation signals with asset exposure and business criticality.

  3. 3
    Remediate

    Follow the vendor advisory or supported update path and preserve rollback options.

  4. 4
    Verify

    Recheck the version, service health, access paths, and relevant logs.

Technical data

CVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:N
CWE
CWE-79