Problem upgrading Craft CMS? When trying to upgrade Craft CMS automatically we get a message relative to the SSL certificate of the CDN being incorrect, though it works fine on a local machine. 


  Craft was unable to install this update :(
  
  [curl] 51: SSL: no alternative certificate subject name matches target
  host name 'download.craftcdn.com' [url]
  https://download.craftcdn.com/craft/2.6/2.6.2967/Patch/2.6.2962/41d682834df8c739ead7a1abab6a4571.zip


Anybody else getting this?
That cURL 51 error usually means that your server doesn't understand the SNI SSL certificate we have installed at https://craftcms.com and https://craftcdn.com.

Technically there are 3 things a server needs to recognize SNI SSL certs:


Using a version of cURL that supports it, at least 7.18.1 (8 years old: https://curl.haxx.se/changes.html)
Using a version of cURL compiled against a library that supports SNI, e.g. OpenSSL 0.9.8j (depending on the compilation options some older versions. 7 years old: https://www.openssl.org/news/changelog.html)
Using TLS 1.0 at least (not SSLv3)


Once the box Craft is on meets those requirements, it should start working.