Yes. 5xx codes are server errors: The server failed to fulfil a valid-looking request.

5xx · Server errorNot part of the HTTP standard

HTTP 523 Origin Is Unreachable

Cloudflare: the origin can't be reached, often a DNS or routing problem.

Example response

HTTP

HTTP/1.1 523 Origin Is Unreachable
Content-Type: application/json; charset=utf-8

{ "error": "Origin Is Unreachable" }

Look up the headers shown here in the HTTP headers reference.

What does HTTP 523 mean?: Origin Is Unreachable. Cloudflare: the origin can't be reached, often a DNS or routing problem.
Is 523 an error?: Yes. 5xx codes are server errors: The server failed to fulfil a valid-looking request.