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GHSA-v3f7-2p4r-mwfw

Keycloak vulnerable to cross-site scripting (xss) via case-insensitive uri validation bypass

Source: GitHub Advisory Database (reviewed) High CVE-2026-9086

Packages

EcosystemPackageAffectedFixed in
Maven org.keycloak:keycloak-services < 26.6.4 26.6.4

Details

As written in the advisory (Markdown source, shown as plain text).

### 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.

References

External links from the advisory. They lead to third-party sites.