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.