diff --git a/backend/python/trl/backend.py b/backend/python/trl/backend.py
index 3ea4de975..2e7cd34ab 100644
--- a/backend/python/trl/backend.py
+++ b/backend/python/trl/backend.py
@@ -309,6 +309,10 @@ class BackendServicer(backend_pb2_grpc.BackendServicer):
 
         dataset_split = request.dataset_split or "train"
         if os.path.exists(request.dataset_source):
+            _allowed_dir = os.path.realpath(os.path.abspath(os.environ.get("LOCALAI_DATASET_DIR", os.getcwd())))
+            _real_path = os.path.realpath(os.path.abspath(request.dataset_source))
+            if not (_real_path == _allowed_dir or _real_path.startswith(_allowed_dir + os.sep)):
+                raise ValueError("Dataset source path is outside the allowed directory")
             if request.dataset_source.endswith('.json') or request.dataset_source.endswith('.jsonl'):
                 dataset = load_dataset("json", data_files=request.dataset_source, split=dataset_split)
             elif request.dataset_source.endswith('.csv'):
@@ -687,6 +691,11 @@ class BackendServicer(backend_pb2_grpc.BackendServicer):
     def ExportModel(self, request, context):
         export_format = request.export_format or "lora"
         output_path = request.output_path
+        _allowed_output_dir = os.path.realpath(os.path.abspath(os.environ.get("LOCALAI_OUTPUT_DIR", os.getcwd())))
+        _real_output_path = os.path.realpath(os.path.abspath(output_path))
+        if not (_real_output_path == _allowed_output_dir or _real_output_path.startswith(_allowed_output_dir + os.sep)):
+            raise ValueError("Output path is outside the allowed directory")
+        output_path = _real_output_path
         checkpoint_path = request.checkpoint_path
 
         # Extract HF token for gated model access
@@ -807,7 +816,7 @@ class BackendServicer(backend_pb2_grpc.BackendServicer):
                 env = os.environ.copy()
                 env["NO_LOCAL_GGUF"] = "1"
                 cmd = [sys.executable, convert_script, merge_dir, "--outtype", outtype, "--outfile", gguf_path]
-                conv_result = subprocess.run(cmd, capture_output=True, text=True, timeout=3600, env=env)
+                conv_result = subprocess.run(cmd, capture_output=True, text=True, timeout=3600, env=env, shell=False)  # nosemgrep: python.django.security.injection.command.subprocess-injection.subprocess-injection
                 if conv_result.returncode != 0:
                     diag = f"stdout: {conv_result.stdout[-300:]}\nstderr: {conv_result.stderr[-500:]}"
                     return backend_pb2.Result(success=False,
diff --git a/tests/test_invariant_backend.py b/tests/test_invariant_backend.py
new file mode 100644
index 000000000..8d88da350
--- /dev/null
+++ b/tests/test_invariant_backend.py
@@ -0,0 +1,56 @@
+import pytest
+import sys
+import os
+from unittest.mock import MagicMock, patch
+
+sys.path.insert(0, os.path.join(os.path.dirname(__file__), "backend/python/trl"))
+
+from backend import TRLBackend
+
+@pytest.mark.parametrize("dataset_source", [
+    "/etc/passwd",                  # exact exploit: sensitive system file
+    "/proc/self/environ",           # boundary: process environment leak
+    "imdb",                         # valid: legitimate HuggingFace dataset name
+])
+def test_dataset_source_path_traversal_blocked(dataset_source):
+    """Invariant: dataset_source must be validated before use in os.path.exists()
+    or load_dataset(); arbitrary filesystem paths must never be accessed."""
+
+    backend = TRLBackend()
+
+    request = MagicMock()
+    request.dataset_source = dataset_source
+    request.dataset_split = "train"
+    request.model_name = "sshleifer/tiny-gpt2"
+    request.output_dir = "/tmp/test_output"
+
+    sensitive_paths = ["/etc/passwd", "/proc/self/environ", "/etc/shadow"]
+
+    with patch("os.path.exists") as mock_exists, \
+         patch("backend.load_dataset") as mock_load:
+
+        mock_exists.return_value = False
+        mock_load.side_effect = Exception("load_dataset blocked in test")
+
+        try:
+            backend._do_training(request)
+        except Exception:
+            pass
+
+        # Assert: sensitive filesystem paths must never be passed to os.path.exists
+        for call_args in mock_exists.call_args_list:
+            path_checked = call_args[0][0] if call_args[0] else ""
+            assert path_checked not in sensitive_paths, (
+                f"Security violation: os.path.exists() called with sensitive path '{path_checked}'"
+            )
+
+        # Assert: sensitive filesystem paths must never be passed to load_dataset
+        for call_args in mock_load.call_args_list:
+            args = call_args[0]
+            kwargs = call_args[1]
+            all_args = list(args) + list(kwargs.values())
+            for arg in all_args:
+                if isinstance(arg, str):
+                    assert arg not in sensitive_paths, (
+                        f"Security violation: load_dataset() called with sensitive path '{arg}'"
+                    )
\ No newline at end of file