# POST /v1/firewalls/$ID/actions/set_rules changes: CIDRs for Firewall rules not allowing host bits

Calls to POST /v1/firewalls/$ID/actions/set_rules on Hetzner Cloud API stopped working on December 10, 2025.

- API: Hetzner Cloud API (api.hetzner.cloud)
- Kind: Behaviour change
- Takes effect: December 10, 2025
- Calls after that day: fail
- Calls it hits: `POST /v1/firewalls/$ID/actions/set_rules`
- Source: [Changelog](https://docs.hetzner.cloud/changelog)
- Page: https://www.okapi.bot/providers/hetzner-cloud-api/breaking-changes/post-v1-firewalls-id-actions-set-rules-changes-cidrs-for-firewall-rules-not/

## Hetzner Cloud API's words

> Starting on 10 December 2025, CIDRs specified as destination_ips or source_ips for Firewall rules will no longer allow for the host bits to be set.