Zone Lockdown

Currently, any Cloudflare customer on a paid plan can configure Health Checks against any host or IP. Zone Lockdown specifies a list of one or more IP addresses, CIDR ranges, or networks that are the only IPs allowed to access a domain, subdomain, or URL. It allows multiple destinations in a single rule as well as IPv4 and IPv6 addresses. IP addresses not specified in the Zone Lockdown rule are denied access to the specified resources.

When a customer enables zone lockdown, any Health Checks targeting that zone regardless of ownership will still get through because Cloudflare’s ASN is on an allow-list.

Cloudflare’s ASN is on an allow-list. This allows health checks to bypass zone lockdown. However, this creates a vulnerability and that behavior will change, resulting in Health Checks no longer being allowed through zone lockdown by default. Customers who use zone lockdown and want their health checks to continue passing can follow the guide below to bypass zone lockdown.

Bypass zone lockdown

To bypass zone lockdown using a WAF custom rule:

1. Log in to the Cloudflare dashboard ↗ and select your account and domain.
2. Go to Security > WAF > Custom rules.
3. Select Create rule.
4. Create a custom rule matching on user agent.
5. Set the action to Skip and the corresponding feature to Zone Lockdown under More components to skip.

Cloudflare Health Checks have a user agent of the following format: Mozilla/5.0 (compatible;Cloudflare-Healthchecks/1.0;+https://www.cloudflare.com/; healthcheck-id: XXX) where XXX is replaced with the first 16 characters of the Health Check ID.

To allow a specific Health Check, verify if the user agent contains the first 16 characters of the Health Check ID.

Via the API

This example adds a new WAF custom rule to the ruleset with ID {ruleset_id} that skips zone lockdown for incoming requests with a user agent containing 1234567890abcdef:

curl "https://api.cloudflare.com/client/v4/{zone_id}/rulesets/{ruleset_id}/rules" \
--header "Authorization: Bearer <API_TOKEN>" \
--header "Content-Type: application/json" \
--data '{
  "action": "skip",
  "action_parameters": {
    "products": [
      "zoneLockdown"
    ]
  },
  "expression": "http.user_agent contains \"1234567890abcdef\"",
  "description": "bypass zone lockdown - specific healthcheck"
}'