Keycloak: keycloak: cross-site scripting (xss) via case-insensitive uri validation bypass
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.
describes (1)
Related CVEs.
| ID | severity | exploitable | ||
|---|---|---|---|---|
| CVE-2026-9086US | — | Exploit | ||
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… | ||||
references
External citations — patches, advisories, analysis.
- https://access.redhat.com/errata/RHSA-2026:30049ADVISORY
- https://access.redhat.com/errata/RHSA-2026:30050ADVISORY
- https://access.redhat.com/errata/RHSA-2026:30083ADVISORY
- https://access.redhat.com/errata/RHSA-2026:30084ADVISORY
- https://access.redhat.com/security/cve/CVE-2026-9086ADVISORY
- https://bugzilla.redhat.com/show_bug.cgi?id=2480170ADVISORY
- https://nvd.nist.gov/vuln/detail/CVE-2026-9086WEB
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-9086.jsonADVISORY
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