Error 522 occurs when Cloudflare times out contacting the origin web server. Two different timeouts cause HTTP error 522 depending on when they occur between Cloudflare and the origin web server:
Before a connection is established, the origin web server does not return a SYN+ACK to Cloudflare within 15 seconds of Cloudflare sending a SYN.
After a connection is established, the origin web server doesn’t acknowledge (ACK) Cloudflare’s resource request within 90 seconds.
(Most common cause) Cloudflare IP addressesOpen external link are rate limited or blocked in .htaccess, iptables, or firewalls. Confirm your hosting provider allows Cloudflare IP addresses.
An overloaded or offline origin web server drops incoming requests.
The origin IP address in your Cloudflare DNS app does not match the IP address currently provisioned to your origin web server by your hosting provider.
If none of the above leads to a resolution, request the following information from your hosting provider or site administrator before contacting Cloudflare support:
An MTR or traceroute from your origin web server to a Cloudflare IP addressOpen external link that most commonly connected to your origin web server before the issue occurred. Identify a connecting Cloudflare IP recorded in the origin web server logs.
Details from the hosting provider’s investigation such as pertinent logs or conversations with the hosting provider.