Improper Access Control vulnerability in ash-project ash lets a create action overwrite an existing record when the ETS or Mnesia data layer is used, because neither enforced primary-key uniqueness on insert.

Unlike a SQL data layer, whose unique primary-key constraint rejects a duplicate, the ETS and Mnesia data layers implemented create as a keyed insert that replaces any existing entry with the same primary key (lib/ash/data_layer/ets/ets.ex, lib/ash/data_layer/mnesia/mnesia.ex). An actor who can set the primary key on a create (for example a user-supplied string or integer key) can submit a create whose key matches an existing record and silently overwrite it, destroying and replacing another entity's data without going through the update action or its policies. The fix rejects a create whose primary key already exists with an already-taken error, and only allows duplicates for keyless resources.

This issue affects ash: from 0.4.0 before 3.32.2.