Apache Airflow's Task SDK rebuilt a "Callback" object from serialized data by re-running its constructor, which imports the module named by the stored callback path. Because "SyncCallback" is itself an Airflow class it passes the default "allowed_deserialization_classes" allow-list, so tightening that setting does not help. A Dag author — who controls a task instance's "next_kwargs" through the task execution API — can therefore cause an arbitrary module to be imported inside the scheduler process, when the scheduler's "awaiting_input" timeout sweep deserializes that value. No non-default configuration is required; the sweep runs unconditionally. Versions before 3.3.0 are not affected: the class existed, but the scheduler sweep that reaches it did not. This is a separate code path from CVE-2026-58076 and CVE-2026-67260, which cover different gadgets reaching deserialization — applying either of those fixes does not address this one. Users are advised to upgrade to apache-airflow 3.3.1 or later.