How to Fix Error 526 Invalid SSL Certificate

The Error 526: Invalid SSL Certificate is a common issue that occurs when Cloudflare is unable to validate the SSL certificate from your web server. This prevents secure HTTPS connections and makes your site inaccessible to visitors. Understanding why this happens and how to resolve it can help keep your website secure and accessible.

What Causes Error 526?

Error 526 occurs when Cloudflare’s Full (Strict) SSL mode is enabled, but the origin server’s SSL certificate is either invalid or misconfigured. Common causes include:

• An expired SSL certificate on the origin server.
• A self-signed SSL certificate that Cloudflare does not trust.
• A missing or improperly installed SSL certificate.
• Incorrect settings in your Cloudflare SSL/TLS configuration.

Step-by-Step Guide to Fix Error 526

Follow these steps to diagnose and resolve the issue:

1. Verify Your SSL Certificate on the Origin Server

The first step is to check the SSL certificate installed on your web server. If it’s expired, invalid, or self-signed, Cloudflare will not recognize it as secure.

• Check Certificate Validity: Use online tools such as SSL Checker or SSL Labs to inspect your certificate.
• Renew Expired Certificates: If your SSL certificate has expired, renew it through your Certificate Authority (CA) or use free options like Let’s Encrypt.
• Replace Self-Signed Certificates: Cloudflare does not trust self-signed certificates in Full (Strict) mode. Use a valid CA-issued certificate instead.

2. Ensure Proper SSL Installation

Sometimes, the SSL certificate is valid but not installed correctly. Verify that the certificate is correctly configured on your server:

• Check the Full Certificate Chain: The server must provide the entire SSL certificate chain, including the intermediate certificates.
• Confirm the Private Key Matches: The SSL certificate should be paired with the correct private key.

If your SSL certificate is not configured correctly, re-upload the correct files, including the certificate, private key, and any required chain files.

3. Adjust Cloudflare SSL/TLS Settings

Cloudflare offers different SSL/TLS modes that dictate how it interacts with your origin server’s SSL certificate:

• Flexible: No SSL required on the origin server (not recommended for security reasons).
• Full: SSL required on the origin, but does not validate the certificate.
• Full (Strict): SSL required and must be valid (this is where Error 526 occurs if there’s an issue).

If you are unable to fix your SSL certificate immediately, you can temporarily switch from Full (Strict) to Full in Cloudflare. However, this is not a permanent fix, and resolving your SSL issues should remain a priority.

4. Use a Cloudflare Origin Certificate

If purchasing or configuring a third-party SSL certificate is difficult, you can use a Cloudflare Origin Certificate instead. This is a certificate issued by Cloudflare that is trusted only by Cloudflare and can be used in Full (Strict) mode.

5. Verify Your Web Server’s SSL Configuration

Your web server’s configuration might be contributing to the error. Ensure that:

• The correct certificate and private key are set up in the server’s SSL settings.
• The server is listening for HTTPS connections on port 443.
• There are no mixed content issues causing Cloudflare to block the SSL handshake.

Conclusion

Fixing Error 526: Invalid SSL Certificate requires ensuring that your origin server has a valid, properly installed SSL certificate. Regularly renewing certificates, using a Cloudflare Origin Certificate, and configuring your server correctly can help prevent this issue from occurring in the future. By following the steps outlined above, you can restore secure HTTPS access to your website efficiently.