diff --git a/swh/indexer/metadata_dictionary/cff.py b/swh/indexer/metadata_dictionary/cff.py
--- a/swh/indexer/metadata_dictionary/cff.py
+++ b/swh/indexer/metadata_dictionary/cff.py
@@ -22,14 +22,19 @@
     mapping = CROSSWALK_TABLE["Citation File Format Core (CFF-Core) 1.0.2"]
     string_fields = ["keywords", "license", "abstract", "version", "doi"]
 
-    def translate(self, raw_content: bytes) -> Dict[str, str]:
+    def translate(self, raw_content: bytes) -> Optional[Dict[str, str]]:
         raw_content_string: str = raw_content.decode()
-        content_dict = yaml.load(raw_content_string, Loader=SafeLoader)
-        metadata = self._translate_dict(content_dict)
+        try:
+            content_dict = yaml.load(raw_content_string, Loader=SafeLoader)
+        except yaml.scanner.ScannerError:
+            return None
 
-        metadata["@context"] = CODEMETA_CONTEXT_URL
+        if isinstance(content_dict, dict):
+            metadata = self._translate_dict(content_dict)
+            metadata["@context"] = CODEMETA_CONTEXT_URL
+            return metadata
 
-        return metadata
+        return None
 
     def normalize_authors(self, d: List[dict]) -> Dict[str, list]:
         result = []
diff --git a/swh/indexer/metadata_dictionary/npm.py b/swh/indexer/metadata_dictionary/npm.py
--- a/swh/indexer/metadata_dictionary/npm.py
+++ b/swh/indexer/metadata_dictionary/npm.py
@@ -136,7 +136,6 @@
     def normalize_description(self, description):
         r"""Try to re-decode ``description`` as UTF-16, as this is a somewhat common
         mistake that causes issues in the database because of null bytes in JSON.
-
         >>> NpmMapping().normalize_description("foo bar")
         'foo bar'
         >>> NpmMapping().normalize_description(
@@ -160,7 +159,7 @@
         >>> NpmMapping().normalize_description(None) is None
         True
         """
-        if description is None:
+        if description is None or type(description) != str:
             return None
         # XXX: if this function ever need to support more cases, consider
         # switching to https://pypi.org/project/ftfy/ instead of adding more hacks
diff --git a/swh/indexer/tests/test_metadata.py b/swh/indexer/tests/test_metadata.py
--- a/swh/indexer/tests/test_metadata.py
+++ b/swh/indexer/tests/test_metadata.py
@@ -159,6 +159,31 @@
         # then
         assert expected == result
 
+    def test_compute_metadata_cff_invalid_yaml(self):
+        """
+        test.yaml translation for invalid yaml file
+        """
+        # given
+        content = """cff-version: 1.0.3
+message: To cite the SigMF specification, please include the following:
+authors:
+  - name: The GNU Radio Foundation, Inc.
+title: The Signal Metadata Format (SigMF)
+version: 0.0.1
+doi: 10.5281/zenodo.1418396
+date-released: 2018-07-18
+license: CC-BY-SA-4.0
+url: https://sigmf.org
+        """.encode(
+            "utf-8"
+        )
+
+        expected = None
+
+        result = self.cff_mapping.translate(content)
+        # then
+        assert expected == result
+
     def test_compute_metadata_npm(self):
         """
         testing only computation of metadata with hard_mapping_npm