diff --git a/glance/async_/flows/plugins/image_conversion.py b/glance/async_/flows/plugins/image_conversion.py
index 32c7b7fe09..e977764fa8 100644
--- a/glance/async_/flows/plugins/image_conversion.py
+++ b/glance/async_/flows/plugins/image_conversion.py
@@ -116,6 +116,29 @@ def _execute(self, action, file_path, **kwargs):
         virtual_size = metadata.get('virtual-size', 0)
         action.set_image_attribute(virtual_size=virtual_size)
 
+        if 'backing-filename' in metadata:
+            LOG.warning('Refusing to process QCOW image with a backing file')
+            raise RuntimeError(
+                'QCOW images with backing files are not allowed')
+
+        if metadata.get('format') == 'vmdk':
+            create_type = metadata.get(
+                'format-specific', {}).get(
+                    'data', {}).get('create-type')
+            allowed = CONF.image_format.vmdk_allowed_types
+            if not create_type:
+                raise RuntimeError(_('Unable to determine VMDK create-type'))
+            if not len(allowed):
+                LOG.warning(_('Refusing to process VMDK file as '
+                              'vmdk_allowed_types is empty'))
+                raise RuntimeError(_('Image is a VMDK, but no VMDK createType '
+                                     'is specified'))
+            if create_type not in allowed:
+                LOG.warning(_('Refusing to process VMDK file with create-type '
+                              'of %r which is not in allowed set of: %s'),
+                            create_type, ','.join(allowed))
+                raise RuntimeError(_('Invalid VMDK create-type specified'))
+
         if source_format == target_format:
             LOG.debug("Source is already in target format, "
                       "not doing conversion for %s", self.image_id)
diff --git a/glance/common/config.py b/glance/common/config.py
index 401751712c..b8f842aad6 100644
--- a/glance/common/config.py
+++ b/glance/common/config.py
@@ -100,6 +100,18 @@
                        "image attribute"),
                 deprecated_opts=[cfg.DeprecatedOpt('disk_formats',
                                                    group='DEFAULT')]),
+    cfg.ListOpt('vmdk_allowed_types',
+                default=['streamOptimized', 'monolithicSparse'],
+                help=_("A list of strings describing allowed VMDK "
+                       "'create-type' subformats that will be allowed. "
+                       "This is recommended to only include "
+                       "single-file-with-sparse-header variants to avoid "
+                       "potential host file exposure due to processing named "
+                       "extents. If this list is empty, then no VDMK image "
+                       "types allowed. Note that this is currently only "
+                       "checked during image conversion (if enabled), and "
+                       "limits the types of VMDK images we will convert "
+                       "from.")),
 ]
 task_opts = [
     cfg.IntOpt('task_time_to_live',
diff --git a/glance/tests/unit/async_/flows/plugins/test_image_conversion.py b/glance/tests/unit/async_/flows/plugins/test_image_conversion.py
index eaa84f43db..393647f6ec 100644
--- a/glance/tests/unit/async_/flows/plugins/test_image_conversion.py
+++ b/glance/tests/unit/async_/flows/plugins/test_image_conversion.py
@@ -172,6 +172,53 @@ def test_image_convert_inspection_reports_error(self):
         # Make sure we did not update the image
         self.img_repo.save.assert_not_called()
 
+    def test_image_convert_invalid_qcow(self):
+        data = {'format': 'qcow2',
+                'backing-filename': '/etc/hosts'}
+
+        convert = self._setup_image_convert_info_fail()
+        with mock.patch.object(processutils, 'execute') as exc_mock:
+            exc_mock.return_value = json.dumps(data), ''
+            e = self.assertRaises(RuntimeError,
+                                  convert.execute, 'file:///test/path.qcow')
+            self.assertEqual('QCOW images with backing files are not allowed',
+                             str(e))
+
+    def _test_image_convert_invalid_vmdk(self):
+        data = {'format': 'vmdk',
+                'format-specific': {
+                    'data': {
+                        'create-type': 'monolithicFlat',
+                    }}}
+
+        convert = self._setup_image_convert_info_fail()
+        with mock.patch.object(processutils, 'execute') as exc_mock:
+            exc_mock.return_value = json.dumps(data), ''
+            convert.execute('file:///test/path.vmdk')
+
+    def test_image_convert_invalid_vmdk(self):
+        e = self.assertRaises(RuntimeError,
+                              self._test_image_convert_invalid_vmdk)
+        self.assertEqual('Invalid VMDK create-type specified', str(e))
+
+    def test_image_convert_valid_vmdk_no_types(self):
+        with mock.patch.object(CONF.image_format, 'vmdk_allowed_types',
+                               new=[]):
+            # We make it past the VMDK check and fail because our file
+            # does not exist
+            e = self.assertRaises(RuntimeError,
+                                  self._test_image_convert_invalid_vmdk)
+            self.assertEqual('Image is a VMDK, but no VMDK createType is '
+                             'specified', str(e))
+
+    def test_image_convert_valid_vmdk(self):
+        with mock.patch.object(CONF.image_format, 'vmdk_allowed_types',
+                               new=['monolithicSparse', 'monolithicFlat']):
+            # We make it past the VMDK check and fail because our file
+            # does not exist
+            self.assertRaises(FileNotFoundError,
+                              self._test_image_convert_invalid_vmdk)
+
     def test_image_convert_fails(self):
         convert = self._setup_image_convert_info_fail()
         with mock.patch.object(processutils, 'execute') as exc_mock: