A flaw was found in Keycloak. The Keycloak guides recommend to not expose /admin path to the outside in case the installation is using a proxy. The issue occurs at least via ha-proxy, as it can be tricked to using relative/non-normalized paths to access the /admin application path relative to /realms which is expected to be exposed.
Credits
Red Hat would like to thank Sebastian Reigber (AEB) for reporting this issue.
