fix: avoid converting None to "None" in AdvisorySeverity

Signed-off-by: Keshav Priyadarshi <git@keshav.space>

Author: keshav-space

vulnerabilities/importer.py

@@ -19,7 +19,6 @@
 from typing import Optional
 from typing import Set
 from typing import Tuple
-from typing import Union
 
 import pytz
 from dateutil import parser as dateparser
@@ -43,7 +42,6 @@
 from vulnerabilities.utils import get_reference_id
 from vulnerabilities.utils import is_commit
 from vulnerabilities.utils import is_cve
-from vulnerabilities.utils import nearest_patched_package
 from vulnerabilities.utils import purl_to_dict
 from vulnerabilities.utils import update_purl_version
 
@@ -68,7 +66,7 @@ def __post_init__(self):
             raise TypeError(f"system must be a ScoringSystem, got {type(self.system)!r}")
 
         if not isinstance(self.value, str):
-            self.value = str(self.value)
+            self.value = str(self.value) if self.value else ""
 
         if self.scoring_elements and self.system in (CVSSV3, CVSSV31, CVSSV4):
             vector_value = self.value

vulnerabilities/migrations/0139_cleanup_none_string_in_severity.py

@@ -0,0 +1,22 @@
+# Generated by Django 5.2.11 on 2026-07-02 09:50
+
+from django.db import migrations
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("vulnerabilities", "0138_fix_malformed_cvss_vector"),
+    ]
+
+    def cleanup_none_severity_string(apps, schema_editor):
+        AdvisorySeverity = apps.get_model("vulnerabilities", "AdvisorySeverity")
+
+        AdvisorySeverity.objects.filter(value="None").update(value="")
+
+    operations = [
+        migrations.RunPython(
+            cleanup_none_severity_string,
+            reverse_code=migrations.RunPython.noop,
+        ),
+    ]

vulnerabilities/models.py

@@ -9,8 +9,6 @@
 
 import csv
 import datetime
-import hashlib
-import json
 import logging
 import uuid
 import xml.etree.ElementTree as ET

vulnerabilities/tests/test_importer.py

@@ -225,3 +225,15 @@ def test_vulnerability_severity_cvss_validation_with_invalid_value():
                 "scoring_elements": "CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N",
             }
         )
+
+
+def test_vulnerability_severity_value_string_conversion():
+    severity = VulnerabilitySeverity.from_dict(
+        {
+            "system": "cvssv3",
+            "value": None,
+            "scoring_elements": "CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N",
+        }
+    )
+
+    assert severity.value == ""