diff --git a/api/apps/sdk/doc.py b/api/apps/sdk/doc.py
index 9aa641ccfc..cf297c4b25 100644
--- a/api/apps/sdk/doc.py
+++ b/api/apps/sdk/doc.py
@@ -116,15 +116,30 @@ async def download_doc(document_id):
     if len(token) != 2:
         return get_error_data_result(message="Authorization is not valid!")
     token = token[1]
+    logging.info("Beta API token lookup attempted for document download")
     objs = APIToken.query(beta=token)
     if not objs:
+        logging.warning("Beta API token lookup failed for document download: invalid API key")
         return get_error_data_result(message='Authentication error: API key is invalid!"')
+    if len(objs) > 1:
+        logging.error("Beta API token lookup is ambiguous for document download: matches=%s", len(objs))
+        return get_error_data_result(message="Authentication error: API key configuration is ambiguous.")
+    tenant_id = objs[0].tenant_id
+    logging.info("Beta API token authorized for document download: tenant_id=%s", tenant_id)
 
     if not document_id:
         return get_error_data_result(message="Specify document_id please.")
     doc = DocumentService.query(id=document_id)
     if not doc:
         return get_error_data_result(message=f"The dataset not own the document {document_id}.")
+    if not KnowledgebaseService.query(id=doc[0].kb_id, tenant_id=tenant_id):
+        logging.warning(
+            "cross-tenant access denied for document download: tenant_id=%s kb_id=%s document_id=%s",
+            tenant_id,
+            doc[0].kb_id,
+            document_id,
+        )
+        return get_error_data_result(message="You do not have access to this document.")
     # The process of downloading
     doc_id, doc_location = File2DocumentService.get_storage_address(doc_id=document_id)  # minio address
     file_stream = settings.STORAGE_IMPL.get(doc_id, doc_location)
diff --git a/test/testcases/test_http_api/test_file_management_within_dataset/test_doc_sdk_routes_unit.py b/test/testcases/test_http_api/test_file_management_within_dataset/test_doc_sdk_routes_unit.py
index 4a6d022c6f..ca440d4ae0 100644
--- a/test/testcases/test_http_api/test_file_management_within_dataset/test_doc_sdk_routes_unit.py
+++ b/test/testcases/test_http_api/test_file_management_within_dataset/test_doc_sdk_routes_unit.py
@@ -516,7 +516,11 @@ class TestDocRoutesUnit:
         res = _run(module.download_doc("doc-1"))
         assert "API key is invalid" in res["message"]
 
-        monkeypatch.setattr(module.APIToken, "query", lambda **_kwargs: [SimpleNamespace()])
+        monkeypatch.setattr(module.APIToken, "query", lambda **_kwargs: [SimpleNamespace(tenant_id="tenant-1"), SimpleNamespace(tenant_id="tenant-2")])
+        res = _run(module.download_doc("doc-1"))
+        assert "API key configuration is ambiguous" in res["message"]
+
+        monkeypatch.setattr(module.APIToken, "query", lambda **_kwargs: [SimpleNamespace(tenant_id="tenant-1")])
         res = _run(module.download_doc(""))
         assert res["message"] == "Specify document_id please."
 
@@ -525,6 +529,23 @@ class TestDocRoutesUnit:
         assert "not own the document" in res["message"]
 
         monkeypatch.setattr(module.DocumentService, "query", lambda **_kwargs: [_DummyDoc()])
+        kb_query_calls = []
+
+        def _deny_kb_query(**kwargs):
+            kb_query_calls.append(kwargs)
+            return []
+
+        monkeypatch.setattr(module.KnowledgebaseService, "query", _deny_kb_query)
+        monkeypatch.setattr(
+            module.File2DocumentService,
+            "get_storage_address",
+            lambda **_kwargs: (_ for _ in ()).throw(AssertionError("storage lookup must not run before tenant authorization")),
+        )
+        res = _run(module.download_doc("doc-1"))
+        assert res["message"] == "You do not have access to this document."
+        assert kb_query_calls == [{"id": "kb-1", "tenant_id": "tenant-1"}]
+
+        monkeypatch.setattr(module.KnowledgebaseService, "query", lambda **_kwargs: [1])
         monkeypatch.setattr(module.File2DocumentService, "get_storage_address", lambda **_kwargs: ("b", "n"))
         _patch_storage(monkeypatch, module, file_stream=b"")
         res = _run(module.download_doc("doc-1"))