In the Samly package before 1.4.0 for Elixir, Samly.State.Store.get_assertion/3 can return an expired session, which interferes with access control because Samly.AuthHandler uses a cached session and does not replace it, even after expiry.
According to WASC, "Insufficient Session Expiration is when a web site permits an attacker to reuse old session credentials or session IDs for authorization."
The product does not properly control the allocation and maintenance of a limited resource.