diff --git a/api/db/services/document_service.py b/api/db/services/document_service.py
index 5d6289e5734..7992cdb6105 100644
--- a/api/db/services/document_service.py
+++ b/api/db/services/document_service.py
@@ -678,17 +678,10 @@ def get_tenant_id_by_name(cls, name):
     @classmethod
     @DB.connection_context()
     def accessible(cls, doc_id, user_id):
-        docs = (
-            cls.model.select(cls.model.id)
-            .join(Knowledgebase, on=(Knowledgebase.id == cls.model.kb_id))
-            .join(UserTenant, on=(UserTenant.tenant_id == Knowledgebase.tenant_id))
-            .where(cls.model.id == doc_id, UserTenant.user_id == user_id)
-            .paginate(0, 1)
-        )
-        docs = docs.dicts()
-        if not docs:
+        e, doc = cls.get_by_id(doc_id)
+        if not e:
             return False
-        return True
+        return KnowledgebaseService.accessible(doc.kb_id, user_id)
 
     @classmethod
     @DB.connection_context()
diff --git a/api/db/services/knowledgebase_service.py b/api/db/services/knowledgebase_service.py
index c66d66a6821..a164287fa4e 100644
--- a/api/db/services/knowledgebase_service.py
+++ b/api/db/services/knowledgebase_service.py
@@ -18,7 +18,7 @@
 from peewee import fn, JOIN
 
 from api.db import TenantPermission
-from api.db.db_models import DB, Document, Knowledgebase, User, UserTenant, UserCanvas
+from api.db.db_models import DB, Document, Knowledgebase, User, UserCanvas
 from api.db.services.common_service import CommonService
 from common.time_utils import current_timestamp, datetime_format
 from api.db.services import duplicate_name
@@ -485,13 +485,21 @@ def accessible(cls, kb_id, user_id):
         #     user_id: User ID
         # Returns:
         #     Boolean indicating accessibility
-        docs = cls.model.select(
-            cls.model.id).join(UserTenant, on=(UserTenant.tenant_id == Knowledgebase.tenant_id)
-                               ).where(cls.model.id == kb_id, UserTenant.user_id == user_id).paginate(0, 1)
-        docs = docs.dicts()
-        if not docs:
+        e, kb = cls.get_by_id(kb_id)
+        if not e:
             return False
-        return True
+
+        if kb.status != StatusEnum.VALID.value:
+            return False
+
+        if kb.tenant_id == user_id:
+            return True
+
+        if kb.permission != TenantPermission.TEAM.value:
+            return False
+
+        joined_tenants = TenantService.get_joined_tenants_by_user_id(user_id)
+        return any(tenant["tenant_id"] == kb.tenant_id for tenant in joined_tenants)
 
     @classmethod
     @DB.connection_context()
@@ -502,10 +510,10 @@ def get_kb_by_id(cls, kb_id, user_id):
         #     user_id: User ID
         # Returns:
         #     List containing dataset information
-        kbs = cls.model.select().join(UserTenant, on=(UserTenant.tenant_id == Knowledgebase.tenant_id)
-                                      ).where(cls.model.id == kb_id, UserTenant.user_id == user_id).paginate(0, 1)
-        kbs = kbs.dicts()
-        return list(kbs)
+        e, kb = cls.get_by_id(kb_id)
+        if not e or not cls.accessible(kb_id, user_id):
+            return []
+        return [kb.to_dict()]
 
     @classmethod
     @DB.connection_context()
@@ -516,10 +524,11 @@ def get_kb_by_name(cls, kb_name, user_id):
         #     user_id: User ID
         # Returns:
         #     List containing dataset information
-        kbs = cls.model.select().join(UserTenant, on=(UserTenant.tenant_id == Knowledgebase.tenant_id)
-                                      ).where(cls.model.name == kb_name, UserTenant.user_id == user_id).paginate(0, 1)
-        kbs = kbs.dicts()
-        return list(kbs)
+        kbs = cls.query(name=kb_name, status=StatusEnum.VALID.value)
+        for kb in kbs:
+            if cls.accessible(kb.id, user_id):
+                return [kb.to_dict()]
+        return []
 
     @classmethod
     @DB.connection_context()
diff --git a/test/unit_test/api/db/services/test_dataset_access_permissions.py b/test/unit_test/api/db/services/test_dataset_access_permissions.py
new file mode 100644
index 00000000000..e3db6d0f2af
--- /dev/null
+++ b/test/unit_test/api/db/services/test_dataset_access_permissions.py
@@ -0,0 +1,119 @@
+#
+#  Copyright 2026 The InfiniFlow Authors. All Rights Reserved.
+#
+#  Licensed under the Apache License, Version 2.0 (the "License");
+#  you may not use this file except in compliance with the License.
+#  You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing, software
+#  distributed under the License is distributed on an "AS IS" BASIS,
+#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#  See the License for the specific language governing permissions and
+#  limitations under the License.
+#
+import sys
+import types
+import warnings
+from types import SimpleNamespace
+
+# xgboost imports pkg_resources and emits a deprecation warning that is promoted
+# to error in our pytest configuration; ignore it for this unit test module.
+warnings.filterwarnings(
+    "ignore",
+    message="pkg_resources is deprecated as an API.*",
+    category=UserWarning,
+)
+
+
+def _install_cv2_stub_if_unavailable():
+    try:
+        import cv2  # noqa: F401
+        return
+    except Exception:
+        pass
+
+    stub = types.ModuleType("cv2")
+
+    stub.INTER_LINEAR = 1
+    stub.INTER_CUBIC = 2
+    stub.BORDER_CONSTANT = 0
+    stub.BORDER_REPLICATE = 1
+    stub.COLOR_BGR2RGB = 0
+    stub.COLOR_BGR2GRAY = 1
+    stub.COLOR_GRAY2BGR = 2
+    stub.IMREAD_IGNORE_ORIENTATION = 128
+    stub.IMREAD_COLOR = 1
+    stub.RETR_LIST = 1
+    stub.CHAIN_APPROX_SIMPLE = 2
+
+    def _missing(*_args, **_kwargs):
+        raise RuntimeError("cv2 runtime call is unavailable in this test environment")
+
+    def _module_getattr(name):
+        if name.isupper():
+            return 0
+        return _missing
+
+    stub.__getattr__ = _module_getattr
+    sys.modules["cv2"] = stub
+
+
+_install_cv2_stub_if_unavailable()
+
+from api.db import TenantPermission
+from api.db.services.document_service import DocumentService
+from api.db.services.knowledgebase_service import KnowledgebaseService
+from common.constants import StatusEnum
+
+
+def _unwrapped_kb_accessible():
+    return KnowledgebaseService.accessible.__func__.__wrapped__
+
+
+def _unwrapped_doc_accessible():
+    return DocumentService.accessible.__func__.__wrapped__
+
+
+def test_private_dataset_is_not_accessible_to_other_tenant_member(monkeypatch):
+    kb = SimpleNamespace(
+        id="kb-private",
+        tenant_id="owner-1",
+        permission=TenantPermission.ME.value,
+        status=StatusEnum.VALID.value,
+    )
+
+    monkeypatch.setattr(KnowledgebaseService, "get_by_id", classmethod(lambda cls, kb_id: (True, kb)))
+    monkeypatch.setattr(
+        "api.db.services.knowledgebase_service.TenantService.get_joined_tenants_by_user_id",
+        lambda _user_id: [{"tenant_id": "owner-1"}],
+    )
+
+    assert _unwrapped_kb_accessible()(KnowledgebaseService, "kb-private", "member-2") is False
+
+
+def test_team_dataset_is_accessible_to_joined_tenant_member(monkeypatch):
+    kb = SimpleNamespace(
+        id="kb-team",
+        tenant_id="owner-1",
+        permission=TenantPermission.TEAM.value,
+        status=StatusEnum.VALID.value,
+    )
+
+    monkeypatch.setattr(KnowledgebaseService, "get_by_id", classmethod(lambda cls, kb_id: (True, kb)))
+    monkeypatch.setattr(
+        "api.db.services.knowledgebase_service.TenantService.get_joined_tenants_by_user_id",
+        lambda _user_id: [{"tenant_id": "owner-1"}],
+    )
+
+    assert _unwrapped_kb_accessible()(KnowledgebaseService, "kb-team", "member-2") is True
+
+
+def test_document_access_respects_dataset_permission(monkeypatch):
+    doc = SimpleNamespace(id="doc-1", kb_id="kb-private")
+
+    monkeypatch.setattr(DocumentService, "get_by_id", classmethod(lambda cls, doc_id: (True, doc)))
+    monkeypatch.setattr(KnowledgebaseService, "accessible", classmethod(lambda cls, kb_id, user_id: False))
+
+    assert _unwrapped_doc_accessible()(DocumentService, "doc-1", "member-2") is False