A reference leak vulnerability exists in the items-view union and subtraction operators of aio-libs/multidict versions 6.7.0 through 6.9.0. This flaw allows a remote client to cause unbounded memory growth by leaking key-identity and value objects during certain set operations on dictionary views. The leak occurs because the code fails to release new strong references created during iteration, leading to unreclaimable memory until the process is terminated. This issue affects servers using aio-libs that build these views over attacker-controlled HTTP headers or query strings.