CVE-2026-3872: Keycloak: Redirect URI validation bypass via ..;/ path traversal in OIDC auth endpoint

A flaw was found in Keycloak. This issue allows an attacker, who controls another path on the same web server, to bypass the allowed path in redirect Uniform Resource Identifiers (URIs) that use a wildcard. A successful attack may lead to the theft of an access token, resulting in information disclosure.