ERR_CERT_COMMON_NAME_INVALID: Domain Mismatch

ERR_CERT_COMMON_NAME_INVALID (NET::ERR_CERT_COMMON_NAME_INVALID) means the requested domain is not listed in the certificate's SAN field. Example: cert issued for example.com but you open www.example.com. Fix: reissue the certificate with both domains in SAN, or use wildcard *.example.com.

The error can appear in Chrome, Edge, Opera, Brave (all Chromium-based), and partially in Firefox and Safari. Different browsers display the same code differently, but the underlying issue is the same.

1. Check the SSL certificate online — the Enterno.io checker shows the grade, expiry, chain, and specific cause.
2. If the issue is server-side — reissue the certificate via certbot or your chosen CA.
3. Update nginx/apache config (enable TLS 1.2/1.3, fullchain, correct ciphers).
4. Check kernel OpenSSL — an outdated openssl < 1.1 can break handshakes.
5. After deploy: recheck via SSL checker + clear the browser SSL cache.

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• NET::ERR_CERT_AUTHORITY_INVALID
• ERR_CERT_DATE_INVALID
• ERR_SSL_PROTOCOL_ERROR
• Mixed Content
• Check SSL certificate online →

The ERR_CERT_COMMON_NAME_INVALID error occurs when the common name (CN) in the SSL certificate does not match the domain name in the URL. To resolve this, ensure that the SSL certificate is correctly configured for your domain. Check the certificate's CN and Subject Alternative Names (SAN) using tools like OpenSSL and update or reissue the certificate as necessary. For example, use the command openssl s_client -connect yourdomain.com:443 to inspect the certificate details.

The ERR_CERT_COMMON_NAME_INVALID error is a common issue encountered when accessing websites secured with SSL/TLS. This error indicates a mismatch between the domain name requested by the user and the common name specified in the SSL certificate. The common name is a critical part of the SSL certificate, which helps establish trust between the user and the server.

When a user navigates to a website, the browser checks the SSL certificate to verify its authenticity. If the common name in the certificate does not match the domain name, the browser will display the ERR_CERT_COMMON_NAME_INVALID error. This can occur for several reasons:

• The SSL certificate was issued for a different domain.
• The certificate has expired or is not yet valid.
• The server is misconfigured, serving the wrong certificate.
• The user is accessing the site through a subdomain that is not covered by the certificate.

To prevent this error from occurring, it is essential to ensure that the SSL certificate is configured correctly and that it covers all necessary domain variations, including www and non-www versions, as well as any subdomains. Regular audits of SSL certificates can help identify potential issues before they affect users.

To fix the ERR_CERT_COMMON_NAME_INVALID error, follow these practical steps:

1. Check the SSL Certificate: Use the following OpenSSL command to verify the certificate details:

openssl s_client -connect yourdomain.com:443 -showcerts

This command will display the certificate chain. Look for the Subject field to identify the common name and ensure it matches your domain.

1. Update the SSL Certificate: If the common name is incorrect, reissue the SSL certificate with the correct domain name. Ensure that the certificate includes all necessary Subject Alternative Names (SAN) to cover variations of your domain.
2. Check Server Configuration: Ensure that your web server is configured to serve the correct SSL certificate. For example, in an Apache server, check the VirtualHost configuration:

<VirtualHost *:443>
    ServerName yourdomain.com
    ServerAlias www.yourdomain.com
    SSLEngine on
    SSLCertificateFile /path/to/your/certificate.crt
    SSLCertificateKeyFile /path/to/your/private.key
    SSLCertificateChainFile /path/to/your/chainfile.pem
</VirtualHost>

1. Clear Browser Cache: After updating the certificate, clear your browser cache or try accessing the site in incognito mode to eliminate cached data that may still trigger the error.
2. Test with Different Browsers: Sometimes, different browsers may handle SSL certificates differently. Test your site on multiple browsers to ensure the issue is resolved across the board.

By following these steps, you can effectively troubleshoot and resolve the ERR_CERT_COMMON_NAME_INVALID error, ensuring a secure and trustworthy experience for your website visitors.