# CVE-2026-42359: Apache Airflow: Authenticated RCE via XCom PATCH endpoint — XComUpdateBody missing FORBIDDEN_XCOM_KEYS validator

Status: published. Published: 2026-06-01. Updated: 2026-11-03.

A bug in Apache Airflow's XCom PATCH endpoint `PATCH /api/v2/xcomEntries/{key}` allowed an authenticated UI/API user with XCom write permission on a Dag to set XCom entries under reserved key names (e.g. `return_value`) that the matching POST endpoint already validated against `FORBIDDEN_XCOM_KEYS`. The endpoint also accepted serialized payload shapes the triggerer's deserializer treats as code; combined, this allowed RCE on the triggerer when the affected task next deferred. Affects deployments where untrusted users have XCom write permission on Dags that defer to the triggerer. This is a fix-bypass of CVE-2026-33858: PR #64148 added the `FORBIDDEN_XCOM_KEYS` validator only on the POST/set path; the PATCH path was not covered. Users who already upgraded for CVE-2026-33858 should additionally upgrade to `apache-airflow` 3.2.2 or later to cover the PATCH-path bypass.

## Remediation

- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: apache) — https://github.com/apache/airflow/pull/65915

## Affected products and versions

- Apache Software Foundation / Apache Airflow (apache-airflow-core): ≥ 3.2.0; < 3.2.2 (affected, semver). Source: CNA: apache

## Severity and prioritization

- CVSS 3.1: 8.8 (high); CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H; source: ADP: CISA-ADP

- CISA KEV: No listing in collected sources

- EPSS: 0.57% as of 2026-11-02; percentile 47.24%

- SSVC: exploitation none; automatable no; technical impact total; source ADP: CISA-ADP

- Weaknesses: CWE-502

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/apache/airflow/pull/65915 (CNA: apache; patch)

- https://lists.apache.org/thread/g8dqykpf1p90tysq8tln4qtkqwb1038s (CNA: apache; vendor-advisory)

- https://www.cve.org/CVERecord?id=CVE-2026-33858 (CNA: apache; related)

## Provenance

- CNA: apache: https://www.cve.org/CVERecord?id=CVE-2026-42359; retrieved 2026-11-03; source updated 2026-11-03

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-42359; retrieved 2026-11-03; source updated Not reported

Revision: a46a89ddb0a497b47a034a32f03ed3b35f1ec45ea22c79795f2245372837b5dc

Canonical: https://y2.dev/cve/CVE-2026-42359

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