{"id":"PYSEC-2026-3991","details":"Apache Airflow's serialization layer reconstructed exception nodes by calling `import_string()` on a class name taken from the serialized blob and instantiating it with arguments from the same blob, with no restriction on what could be imported. An operator's `executor_config` reaches that branch, so a Dag author could place a value there that causes an arbitrary callable to be imported and invoked -- for example `subprocess.check_output`, or `builtins.eval` on the `builtins`-prefixed variant. The code runs in the **Scheduler**, which reconstructs serialized Dags in its normal loop with no request involved, and in the **API server**, on any authenticated read of the Dag such as `GET /api/v2/dags/{dag_id}/details`. Both are components the Airflow security model states must never execute Dag-author code, and both hold the metadata database credentials and the JWT signing secret. No non-default configuration is required. This is a **different sink from CVE-2026-33264**, which covered only the trigger branch of the same deserializer: deployments that upgraded in response to that advisory are still affected through the exception branch and must upgrade again. Users are advised to upgrade to apache-airflow 3.3.1 or later, which restricts the imported class to a subclass of `BaseException`.","aliases":["BIT-airflow-2026-58076","CVE-2026-58076"],"modified":"2026-09-28T10:25:33.876408657Z","published":"2026-08-12T16:17:08.317Z","references":[{"type":"WEB","url":"https://www.cve.org/CVERecord?id=CVE-2026-33264"},{"type":"ADVISORY","url":"https://lists.apache.org/thread/t81p688t15jozxsng8521o60nh2kfsos"},{"type":"FIX","url":"https://github.com/apache/airflow/pull/68511"}],"affected":[{"package":{"name":"apache-airflow","ecosystem":"PyPI","purl":"pkg:pypi/apache-airflow"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"3.3.0"},{"fixed":"3.3.1"}]}],"versions":["3.3.0","3.3.1rc1","3.3.1rc2"],"ecosystem_specific":{},"database_specific":{"source":"https://github.com/pypa/advisory-database/blob/main/vulns/apache-airflow/PYSEC-2026-3991.yaml"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"}]}