Security improvements for SSH
By Steven Van ·
Old RSA-SHA1 keys and a legacy Diffie-Hellman method are being phased out on a set schedule through January 2026.
GitHub is tightening SSH connections for GitHub ahead of a phased rollout starting October 14, 2026. From that date, all new RSA SSH keys must be at least 3072 bits, for both signing and authentication. GitHub is also removing the ssh-rsa signature type (RSA keys using SHA-1, including ssh-rsa-cert-v01@openssh.com certificates) and the diffie-hellman-group-exchange-sha256 key exchange mechanism, and adding support for the post-quantum key exchange method mlkem768x25519-sha256 on github.com and GitHub Enterprise Cloud with Data Residency, except the U.S. region.
Only users connecting over SSH, or using the unauthenticated Git protocol on GitHub Enterprise Server, are affected; remotes starting with https:// are untouched. Existing RSA keys don't need to be regenerated as long as the client supports RSA with SHA-2 (rsa-sha2-256 or rsa-sha2-512), which most current SSH software uses automatically; GitHub lists minimum versions including OpenSSH 7.2p1, PuTTY 0.82, and libssh2 1.11.0. Users on older software can switch to an Ed25519 or ECDSA key instead.
- November 4, 2026: first brownout of ssh-rsa and diffie-hellman-group-exchange-sha256
- December 9, 2026: second brownout of the same
- January 13, 2026: both are removed entirely
These changes land in GitHub Enterprise Server 3.25, except for mlkem768x25519-sha256 support, which arrives in 3.24. Full details are in the original announcement.
