https://seclists.org/oss-sec/2026/q4/594: CVE-2026-111421: Apache Airflow: Execution API: set_xcom skips the reserved-key check, so task-written XComs instantiate airflow.* classes on the API server

Q: Which deployments are affected?

Apache Airflow versions 3.0.0 before 3.4.0 are affected. This includes deployments running 3.3.1 that applied the fix for CVE-2026-59242, because the Task Execution API route remained vulnerable.

Q: What does an attacker need to exploit this issue?

The attacker needs to be able to author a DAG task that writes an XCom value. Exploitation occurs when a user later views that XCom through the API with deserialization enabled.

Q: What is the security impact when exploitation succeeds?

A DAG author can cause the API server to instantiate classes in the airflow.* namespace using arguments chosen by that author. The issue results from the Task Execution API not applying the reserved-key check when storing task-written XCom values.

Q: What should teams do to remediate the issue?

Upgrade Apache Airflow to version 3.4.0 or later. The advisory specifically notes that applying only the prior CVE-2026-59242 fix on version 3.3.1 does not remediate this route.

Published Nov 9, 2026

Updated

Affected Software

1 affected component

Apache Airflow>=3.0.0<3.4.0

Frequently Asked Questions

Which deployments are affected?

Apache Airflow versions 3.0.0 before 3.4.0 are affected. This includes deployments running 3.3.1 that applied the fix for CVE-2026-59242, because the Task Execution API route remained vulnerable.

What does an attacker need to exploit this issue?

The attacker needs to be able to author a DAG task that writes an XCom value. Exploitation occurs when a user later views that XCom through the API with deserialization enabled.

What is the security impact when exploitation succeeds?

A DAG author can cause the API server to instantiate classes in the airflow.* namespace using arguments chosen by that author. The issue results from the Task Execution API not applying the reserved-key check when storing task-written XCom values.

What should teams do to remediate the issue?

Upgrade Apache Airflow to version 3.4.0 or later. The advisory specifically notes that applying only the prior CVE-2026-59242 fix on version 3.3.1 does not remediate this route.

https://seclists.org/oss-sec/2026/q4/594: CVE-2026-111421: Apache Airflow: Execution API: set_xcom skips the reserved-key check, so task-written XComs instantiate airflow.* classes on the API server

Affected Software

Frequently Asked Questions

Which deployments are affected?

What does an attacker need to exploit this issue?

What is the security impact when exploitation succeeds?

What should teams do to remediate the issue?

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Frequently Asked Questions

Which deployments are affected?

What does an attacker need to exploit this issue?

What is the security impact when exploitation succeeds?

What should teams do to remediate the issue?