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Troubleshooting

Troubleshooting TLS Handshake Failures

Diagnose TLS handshake failures caused by protocol, cipher, certificate, or network problems.

CertOne1 min read

Handshake failures are common TLS connection problems. This guide explains how to diagnose and resolve them.

1. Causes of handshake failure​

1. Protocol mismatch​

The client and server do not support a common TLS version.

2. Cipher suite mismatch​

The client and server have no cipher suite in common.

3. Certificate problems​

The certificate is expired, invalid, or untrusted.

4. Network problems​

The connection is unstable or blocked by a firewall.

2. Diagnosis​

1. Test with OpenSSL​

openssl s_client -connect example.com:443 -servername example.com

2. Review server logs​

Check the NGINX or Apache error logs.

3. Use a TLS testing tool​

Test the TLS configuration with SSL Labs.

3. Resolution​

1. Protocol problems​

Ensure that the server supports a secure TLS version also supported by the client.

2. Cipher suite problems​

Configure mutually supported secure cipher suites on the server.

3. Certificate problems​

Renew the certificate or replace it with one from a trusted CA.

4. Network problems​

Check network connectivity and firewall settings.

Conclusion​

Handshake failures usually result from incompatible protocols or ciphers, certificate problems, or network issues. Targeted checks help identify and correct the cause.