OS X 10.10 Yosemite ships with OpenSSH_6.2p2.

Use Homebrew [1] to install 6.6p1 with its bug fixes and enhancements:

    brew install openssh --with-brewed-openssl --with-keychain-support

[1]http://brew.sh

Reference: How to Update OpenSSH on Mac OS X at http://www.dctrwatson.com/2013/07/how-to-update-openssh-on-m...