525 SSL handshake failed
HTTP response status code 525 SSL handshake failed is an unofficial server error that is specific to Cloudflare. This HTTP status code occurs when a HTTP Connection to the origin server is unsuccessful because the SSL handshake fails.
Usage
Cloudflare is a content delivery network that acts as a gateway between a user and a website server. When the 525 SSL handshake failed status code is received, the HTTP Connection between Cloudflare and the origin server has failed due to an error that occurred in the certificate verification process. As such, Cloudflare is unable to create a secure HTTP Connection to the origin server.
Takeaway
The 525 SSL handshake failed status code is a Cloudflare-specific server error that is generated because Cloudflare was not able to create a secure HTTP Connection using SSL due to a failed SSL handshake.