This error happens where there’s a problem validating the SSL certificate on the origin web server and the Cloudflare SSL configuration on the website is set to “Full SSL (Strict)”.
Some of the common causes of this are:
- The certificate has expired
- The certificate has been revoked
- The certificate is self-signed
- Your website configuration is serving a certificate for the wrong domain
sequenceDiagram
participant User
participant Cloudflare
participant Website
Note right of Website: Behind Cloudflare
User->>Cloudflare: Initial request
Cloudflare -->> Website: Server fails SSL validation
Cloudflare -->> User: Returns 526 error