Apache Airflow scheduler: task-written XCom values are fully deserialized in the scheduler process

Impact

While evaluating task dependencies, the scheduler fully deserializes XCom values written by task code. A Dag author controls what tasks write to XCom, so they control data that gets deserialized inside the scheduler. Airflow's security model reserves that context for code installed by the Deployment Manager, above the worker-scoped execution a Dag author is documented to have. This matters to deployments that treat Dag authors as less trusted than the platform team.

Who can reach it

A Dag author who can deploy a Dag. The scheduler must be evaluating a task dependency that reads a task-written XCom value. Authentication (Dag deployment rights) is required.

What to do

Upgrade to apache-airflow 3.4.0 or later and restart the scheduler. 3.4.0 restricts dependency evaluation to primitive XCom values.

References

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