How to Fix: Getting SSL certificate error on valid certificate when accessing via Curl

This issue is affecting users who are trying to access a service using curl on systems running different versions of Ubuntu, such as 14.04 and 18.04, when they have a valid wildcard SSL certificate for *.mysite.com.

It can be frustrating because the error message may not clearly indicate the root cause of the problem, leading to additional troubleshooting efforts.

💡 Why You Are Getting This Error

• The primary reason for this issue is that the CA bundle used by curl on older systems (Ubuntu 14.04) does not include the certificate authority's (CA) root certificate, which is required to validate the SSL certificate of service.mysite.com. This can be due to the fact that the CA bundle received from the SSL provider may not contain all the necessary root certificates for older systems.
• An alternative reason could be that there are other issues with the SSL certificate or the system's configuration, such as a mismatch between the certificate's subject and the domain name being accessed.

🛠️ Step-by-Step Verified Fixes

💡 Conclusion

To resolve this issue, update curl to version 7.64.0-1ubuntu2.4 or later and use the latest CA bundle available from the SSL provider's website. Alternatively, configure a custom CA file on each system that includes all necessary root certificates for the SSL provider's CA bundle.