OpenSSH is a 100% complete SSH 2.0 protocol implementation that includes sftp client and server support. This release contains some changes that may affect your existing configuration:
* ssh(1), sshd(8), ssh-add(1), ssh-keygen(1): an exploitable integer overflow bug was found in the private key parsing code for the XMSS key type. This key type is still experimental and support for it is not compiled by default. No user-facing autoconf option exists in portable OpenSSH to enable it. This bug was found by Adam Zabrocki and reported via SecuriTeam’s SSD program.
* ssh(1), sshd(8), ssh-agent(1): add protection for private keys at rest in RAM against speculation and memory side-channel attacks like Spectre, Meltdown and Rambleed. This release encrypts private keys when they are not in use with a symmetric key that is derived from a relatively large “prekey” consisting of random data (currently 16KB).
This release includes a number of changes that may affect existing configurations:
* ssh-keygen(1): when acting as a CA and signing certificates with an RSA key, default to using the rsa-sha2-512 signature algorithm. Certificates signed by RSA keys will therefore be incompatible with OpenSSH versions prior to 7.2 unless the default is overridden (using “ssh-keygen -t ssh-rsa -s …”).
More info, you can view here.