AES-CTR-256 is only available since OpenSSL v1.0.1. It's possible to view the encoding ciphers by issueing the following command
openssl enc help
It will show all the available encoding ciphers. To check the current version of OpenSSL run the following command
Note that the 0.9.8, 1.0.0 and 1.0.1 branches have been maintained in parallel. OpenSSL 0.9.8zc might be newer than 1.0.1e, so focus on the version instead of the date.
Some applications (i.e. Ruby) don't use the openssl executable, but link to
libssl instead and inherit the abilities of the library. Upgrading OpenSSL to a newer version doesn't help much in that case. If the application uses dynamic linking, then it might suffice to upgrade
libssl to a newer version. If it's linked statically, then the entire application needs to be recompiled with a newer
libssl (or you might check if there is a newer version).
Ruby programmer's can check which OpenSSL version is installed by issueing the following command
ruby -ropenssl -e 'puts OpenSSL::OPENSSL_VERSION'