no matching host key type found. Their offer: ssh-rsa — how to fix

Unable to negotiate with 192.168.1.10 port 22: no matching host key type found. Their offer: ssh-rsa,ssh-dss

Quick fix: Allow it for that host only: ssh -o HostKeyAlgorithms=+ssh-rsa -o PubkeyAcceptedAlgorithms=+ssh-rsa user@host, or permanently in ~/.ssh/config under Host oldbox. Better: upgrade the server's OpenSSH and give it an ed25519 host key.

What it means

During connection setup the client and server must agree on a host key algorithm. Since OpenSSH 8.8 (2021), the client no longer accepts ssh-rsa — RSA signatures with SHA-1, which is considered broken. The newer rsa-sha2-256 / rsa-sha2-512 algorithms use the same RSA key with SHA-2, but very old servers (OpenSSH < 7.2, Dropbear on routers, old switches, some embedded devices) only know ssh-rsa. ssh-dss (DSA) has been disabled even longer.

"Their offer" lists what the server supports. If nothing in it is enabled on your side, negotiation fails.

Fix 1: allow ssh-rsa for one connection

ssh -o HostKeyAlgorithms=+ssh-rsa -o PubkeyAcceptedAlgorithms=+ssh-rsa user@192.168.1.10

HostKeyAlgorithms – lets you accept the server's ssh-rsa host key (fixes this error).
PubkeyAcceptedAlgorithms – lets you authenticate with your RSA key using SHA-1 signatures. Without it you may get past this error and then hit Permission denied (publickey).

On OpenSSH older than 8.5 the second option is called PubkeyAcceptedKeyTypes.

Fix 2: make it permanent for that host only

# ~/.ssh/config
Host oldrouter
    HostName 192.168.1.10
    User admin
    HostKeyAlgorithms +ssh-rsa
    PubkeyAcceptedAlgorithms +ssh-rsa

Then ssh oldrouter. Don't put this under Host *; keep the weakened setting limited to the legacy device.

For Git remotes on an old server, the same Host block works with the Git host name, or set it per command:

GIT_SSH_COMMAND="ssh -o HostKeyAlgorithms=+ssh-rsa -o PubkeyAcceptedAlgorithms=+ssh-rsa" git pull

Very old servers often fail at other steps too:

Unable to negotiate ... no matching key exchange method found. Their offer: diffie-hellman-group1-sha1
Unable to negotiate ... no matching cipher found. Their offer: aes128-cbc,3des-cbc

Enable those the same way, only for that host:

ssh -o KexAlgorithms=+diffie-hellman-group1-sha1 -o Ciphers=+aes128-cbc user@host

Fix 3: upgrade the server (proper fix)

If you control the server, update OpenSSH (7.2+ supports rsa-sha2-*) and add a modern host key:

sudo ssh-keygen -t ed25519 -f /etc/ssh/ssh_host_ed25519_key -N ''
# ensure sshd_config contains:  HostKey /etc/ssh/ssh_host_ed25519_key
sudo systemctl restart ssh        # or sshd

For network devices, check for a firmware update that brings a newer SSH stack.

Client side: switch your own key to ed25519

If the server is modern but rejects your old RSA key setup, generate a new key and install it:

ssh-keygen -t ed25519 -C "me@laptop"
ssh-copy-id -i ~/.ssh/id_ed25519.pub user@host

Check what your client supports

ssh -Q HostKeyAlgorithms
ssh -Q PubkeyAcceptedAlgorithms
ssh -vvv user@host 2>&1 | grep -i 'host key algorithms'

RHEL / Fedora crypto policies

On RHEL 9 and Fedora, the system-wide crypto policy also blocks SHA-1. Per-host options may not be enough; for a temporary workaround use sudo update-crypto-policies --set DEFAULT:SHA1 (and revert later), or LEGACY as a last resort.

Last updated 2026-11-04.