CVE-2026-104874 is a memory leak vulnerability in the items-view union and subtraction operators of the aio-libs/multidict library versions 6.7.0 through 6.9.0. The flaw causes unbounded memory growth by leaking references to key-identity and value objects during certain set operations on dictionary views. This leak occurs because the code fails to release new strong references created during parsing, leading to unreclaimable memory usage that grows until the process is terminated.