A flaw was found in Keycloak that occurs from an error in the re-authentication mechanism within org.keycloak.authentication. This flaw allows hijacking an active Keycloak session by triggering a new authentication process with the query parameter "prompt=login," prompting the user to re-enter their credentials. If the user cancels this re-authentication by selecting "Restart login," an account takeover may occur, as the new session, with a different SUB, will possess the same SID as the previous session.
CWE-287 Improper Authentication