Fixes #12412: Device/VM interface MAC addresses can be nullified via REST API

netbox/dcim/api/serializers.py

@@ -904,7 +904,11 @@ class InterfaceSerializer(NetBoxModelSerializer, CabledObjectSerializer, Connect
     )
     count_ipaddresses = serializers.IntegerField(read_only=True)
     count_fhrp_groups = serializers.IntegerField(read_only=True)
-    mac_address = serializers.CharField(required=False, default=None)
+    mac_address = serializers.CharField(
+        required=False,
+        default=None,
+        allow_null=True
+    )
     wwn = serializers.CharField(required=False, default=None)
 
     class Meta:

netbox/virtualization/api/serializers.py

@@ -126,7 +126,11 @@ class VMInterfaceSerializer(NetBoxModelSerializer):
     l2vpn_termination = NestedL2VPNTerminationSerializer(read_only=True, allow_null=True)
     count_ipaddresses = serializers.IntegerField(read_only=True)
     count_fhrp_groups = serializers.IntegerField(read_only=True)
-    mac_address = serializers.CharField(required=False, default=None)
+    mac_address = serializers.CharField(
+        required=False,
+        default=None,
+        allow_null=True
+    )
 
     class Meta:
         model = VMInterface