How to Fix Cloudflare SSL Cypher Error/Mismatch

When migrating a domain to Cloudflare, you might encounter unexpected SSL/TLS handshake errors that can cause temporary downtime. Here's what these errors mean and how to handle them.

On Firefox:

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SSL_ERROR_NO_CYPHER_OVERLAP

On Google Chrome:

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ERR_SSL_VERSION_OR_CIPHER_MISMATCH

Using curl:

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bash# curl -I https://yourdomain.com

curl: (35) LibreSSL/3.3.6: error:1404B410:SSL routines:ST_CONNECT:sslv3 alert handshake failure

What These Errors Mean

These errors indicate a mismatch between server and client cipher suite to use for the SSL connection, and may have a few possibilities:

Why These Errors Occur

In Cloudflare's Full (Strict) SSL mode, two separate SSL/TLS connections are required:

• Client to Cloudflare (using Cloudflare's Universal SSL certificate)
• Cloudflare to your origin server (using your server's SSL certificate)

When you first add a domain to Cloudflare, the Universal SSL certificate isn't immediately available - it needs to be generated and validated. During this pending period (which takes 5-15 minutes on average):

How to Fix These SSL Cipher Mismatch Errors

If you've recently added your domain to Cloudflare with Full (Strict) SSL as recommended, it's likely these errors are caused by Cloudflare's Universal SSL pending validation:

On your Cloudflare dashboard, navigate to SSL/TLS > Edge Certificates to check the status of your Universal SSL certificate.

This typically takes 5-10 to validate, after which you'll see the status update to Active:

Now you can check your SSL/TSL handshake by sending a curl HTTP HEAD request:

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bashcurl -I https://yourdomain.com

If successful, you should see a successful response:

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bashHTTP/2 200
date: Sat, 22 Feb 2025 15:13:50 GMT
content-type: text/html; charset=utf-8
cache-control: s-maxage=31536000, stale-while-revalidate
vary: Accept-Encoding
cf-cache-status: DYNAMIC
server: cloudflare
# rest of headers

The SSL/TLS handshake errors causing the cipher mismatch disappear after validation because:

If the error persists, you'll need to troubleshoot further:

• Check your client's supported SSL/TLS versions and cipher suites
• Verify the server's SSL/TLS configuration
• Ensure both sides have at least one compatible cipher suite
• Try updating your client's SSL libraries and use various browsers
• You can use OpenSSL to check the server's supported ciphers:

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bashopenssl s_client -connect yourdomain.com:443

How to Prevent These Errors in the Future

There are two main strategies to avoid downtime caused by these SSL errors while migrating a domain to Cloudflare:

1. Pre-provision the Universal SSL certificate before changing nameservers:

• Add the domain to Cloudflare but keep it in DNS-only mode initially
• Wait for the Universal SSL certificate to be validated (5-15 minutes)
• Only then should you change your nameservers to point to Cloudflare

2. Use Flexible SSL mode temporarily:

• Start with Flexible SSL during the migration (usually the default)
• Wait for the Universal SSL certificate to be validated, before switching to Full (Strict) SSL

Note

Flexible SSL is less secure than Full (Strict) SSL, so method 1 of pre-provisioning the Universal SSL certificate is generally recommended to avoid this lessened security during the transition period.

In summary, if you've recently migrated a site to Cloudflare and experience these SSL cipher mismatch errors, waiting for the Universal SSL certificate to validate is often the correct solution.

But for future migrations to Cloudflare, you can prevent this SSL cipher suite mismatch by pre-provisioning the Universal SSL cert before changing nameservers.

Hope this helps!