Multiple Prefixe Object Type Triggers ValueError

[MrPaulAR]

Plugin Version

0.3.1

NetBox Version

v4.4.0-Docker-3.4.0

Python Version

3.12

Steps to Reproduce

No other plugins are installed. No pending migrations.

Created a custom object type called "vrf" with the following fields

• cidr: multiple objects of IPAM -> Prefix
• name: text

Created a custom object from the vrf above

• name: "whatever"
• prefix: I chose 4 random prefixes

The result of clicking add is the traceback below. I get the same result when attempting to view the list of vrf custom objects.

<h1>ValueError
       at /plugins/custom-objects/vrf/add/</h1>
  <pre class="exception_value">Cannot assign "&lt;PrefixQuerySet [&lt;Prefix: 100.87.19.32/27&gt;, &lt;Prefix: 100.87.32.0/21&gt;, &lt;Prefix: 100.87.42.0/23&gt;, &lt;Prefix: 100.87.120.0/23&gt;]&gt;": "Table8Model.cidr" must be a "Prefix" instance.</pre>
  
Request Method: | POST
-- | --
https://redated/plugins/custom-objects/vrf/add/
5.2.5
ValueError
Cannot assign "<PrefixQuerySet [<Prefix: 100.87.19.32/27>, <Prefix: 100.87.32.0/21>, <Prefix: 100.87.42.0/23>, <Prefix: 100.87.120.0/23>]>": "Table8Model.cidr" must be a "Prefix" instance.
/opt/netbox/venv/lib/python3.12/site-packages/django/db/models/fields/related_descriptors.py, line 291, in __set__
netbox_custom_objects.views.CustomObjectEditView
/opt/netbox/venv/bin/python
3.12.3
['/opt/netbox/netbox/',  '/usr/lib/python312.zip',  '/usr/lib/python3.12',  '/usr/lib/python3.12/lib-dynload',  '/opt/netbox/venv/lib/python3.12/site-packages']
Mon, 08 Sep 2025 18:38:45 +0000

Expected Behavior

A custom object is viewable when multiple prefixes are linked to it.

Observed Behavior

A ValueError exception was raised

[arthanson]

Thank you for opening a bug report. I was unable to reproduce the reported behavior with Custom Objects v0.3.1. Please re-confirm the reported behavior on the current stable release and adjust your post above as necessary. Remember to provide detailed steps that someone else can follow using a clean installation of NetBox to reproduce the issue. Remember to include the steps taken to create any initial objects or other data.

[mrmrcoleman]

I tested at:

NetBox: 4.4.0
Custom Objects: 0.3.1

---

It works correctly for me.

[MrPaulAR]

I'm running v4.4.1 and custom objects 0.3.1 running on EKS. My build for the dockerfile is

FROM netboxcommunity/netbox:v4.4.1-3.4.0
RUN uv pip install netboxlabs-netbox-custom-objects==0.3.1

Just for kicks I removed all custom-objects tables from the DB and reran the migrations

ubuntu@netbox-b9bc4b4f7-969x8:/opt/netbox/netbox$ python manage.py migrate netbox_custom_objects
🧬 loaded config '/etc/netbox/config/configuration.py'
🧬 loaded config '/etc/netbox/config/extra.py'
🧬 loaded config '/etc/netbox/config/logging.py'
🧬 loaded config '/etc/netbox/config/plugins.py'
Registering denormalized field <class 'dcim.models.cables.CableTermination'>._device
Registering denormalized field <class 'dcim.models.cables.CableTermination'>._rack
Registering denormalized field <class 'dcim.models.cables.CableTermination'>._location
Registering denormalized field <class 'ipam.models.ip.Prefix'>._site
Registering denormalized field <class 'ipam.models.ip.Prefix'>._location
Operations to perform:
  Apply all migrations: netbox_custom_objects
Running migrations:
  Applying netbox_custom_objects.0001_initial... OK
  Applying netbox_custom_objects.0002_customobjecttype_version... OK

I then performed the steps listed in the original issue and when I created a vrf custom object I was given this error when clicking "create".

ImproperlyConfigured at /plugins/custom-objects/vrfs/add/

Field name `name` is not valid for model `Table1Model` in `netbox_custom_objects.api.serializers.Table1ModelSerializer`.

Request Method: 	POST
Request URL: 	https://hostname/plugins/custom-objects/vrfs/add/
Django Version: 	5.2.6
Exception Type: 	ImproperlyConfigured
Exception Value: 	

Field name `name` is not valid for model `Table1Model` in `netbox_custom_objects.api.serializers.Table1ModelSerializer`.

Exception Location: 	/opt/netbox/venv/lib/python3.12/site-packages/rest_framework/serializers.py, line 1369, in build_unknown_field
Raised during: 	netbox_custom_objects.views.CustomObjectEditView
Python Executable: 	/opt/netbox/venv/bin/python
Python Version: 	3.12.3
Python Path: 	

['/opt/netbox/netbox/',
 '/usr/lib/python312.zip',
 '/usr/lib/python3.12',
 '/usr/lib/python3.12/lib-dynload',
 '/opt/netbox/venv/lib/python3.12/site-packages']

Server time: 	Wed, 17 Sep 2025 15:17:04 +0000