Cloudflare error 526 triggers when Cloudflare is unable to validate server’s SSL/TLS certificate. Let’s fix it now. As a part of our Server Management Services, we help our customers to fix similar Cloudflare related errors regularly.

Overview

1. What is Cloudflare Error 526?
2. What are the Causes of Cloudflare Error 526?
3. How to Fix Cloudflare Error 526?
4. Conclusion

What is Cloudflare Error 526?

While we use Cloudflare, it involves two SSL/TLS certificates. One is provided by Cloudflare and the other by the origin server. The First certificate shown in the browser while visiting the website is the Cloudflare one. Origin server’s certificate protects data exchanges between the server and Cloudflare.

The Full (strict) mode SSL option ensures a secure connection between both the visitor –  Cloudflare domain and Cloudflare – origin web server connections. Thus if any of it fail to establish a secure connection, it triggers the 526 error as shown below.

Let us now look at the possible reasons for this error.

What are the Causes of Cloudflare Error 526?

As we discussed earlier, the error 526 triggers when either the certificate provided by Cloudflare or by the origin server fails to establish a secure connection. This generally happens when:

* Cloudflare cannot validate the SSL certificate at the origin web server
* Full SSL (Strict) SSL is set in the Cloudflare SSL/TLS app.

Let us now look at the steps to fix this error.

How to Fix Cloudflare Error 526?

Full (strict) mode is the most common reason for the 526 error. A quick fix to solve it would be to change the SSL mode to Full instead of Full (strict) from the Overview tab of Cloudflare SSL/TLS section for the particular domain.

If the issue persists even after changing the SSL mode to Full, then it would be more likely related to the origin web server’s SSL certificates. We need to verify that:

1. The certificate is not expired
2. The certificate is not revoked
3. The certificate is signed by a Certificate Authority such as GlobalSign, Verisign, GeoTrust, Comodo, etc, and is not a self-signed SSL certificate.
4. The requested domain name and hostname are in the certificate’s Common Name or Subject Alternative Name.
5. Origin web server accepts connections over port SSL port 443
6. Temporarily pause Cloudflare and cross-check the certificate with any SSL verification sites like  https://www.sslshopper.com to verify that no issues exist with the origin SSL certificate.

If the origin server is using an expired, revoked or self -signed certificate, the next step to fix this error would be to install a proper SSL certificate signed by a Certificate Authority. Likewise, it is important to have the requested domain name and hostname in the certificate’s Common Name or Subject Alternative Name. If we have added a CNAME for the hostname on Cloudflare, the Common Name or SAN may also match the CNAME target.

Cloudflare can also issue origin certificates to us on request if we don’t want to pay for or acquire one from a third-party. The 526 error should disappear after the installation of a valid certificate on the origin server and the server it accept secure (HTTPS) connections.

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Conclusion

In short, Cloudflare error 526 occurs when Cloudflare is unable to validate the server’s SSL/TLS certificate. Today, we saw how our Support Engineers fix this error.