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

The Brief

Apache Airflow's Task Execution API stored task-written XCom values without the reserved-key check that is applied elsewhere.
As a result, task-written XComs can instantiate airflow.* classes on the API server.
Affected versions are Apache Airflow 3.0.0 before 3.4.0; the source rates severity as moderate.

Why it matters

Deployments of Apache Airflow 3.0.0 to before 3.4.0 can have the API server instantiate airflow.* classes from task-written XComs, so teams running those versions should upgrade.

Who’s affected

Teams running Apache Airflow 3.0.0 before 3.4.0
Operators of Airflow API servers that accept task-written XComs

What to do

Upgrade Apache Airflow to 3.4.0 or later

Apache Airflow 3.0.0
Apache Airflow 3.4.0
CVE-2026-111421
#airflow
#security
#vulnerability
#xcom
#apache
#cve-2026-111421

Posted by Rahul Vats on Nov 08 Severity: moderate Affected versions: - Apache Airflow 3.0.0 before 3.4.0 Description: Apache Airflow's Task Execution API stored XCom values written by a task without the reserved-key check applied elsewhere, so a Dag author's task could…

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Timeline

Nov 8
Vulnerability posted to oss-sec by Rahul Vats
Nov 9 · 7:22 AM
Open Source Security
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