I think that would depend on how cURL is built, and not curl itself. OpenSSL 0.9.8 versions (still widely deployed) did not support TLS 1.[12], I think that was

I think that would depend on how cURL is built, and not curl itself. OpenSSL 0.9.8 versions (still widely deployed) did not support TLS 1.[12], I think that was added in 1.0.1c. You can check which version of OpenSSL curl is using by doing $ curl -V