MacDebug

Verified for macOS Tahoe 26.2

Fix Guide: macOS Tahoe SSH "ssh-dss" Connection Errors

Symptom: When trying to connect to older servers or network hardware, you get the error: "no matching host key type found. Their offer: ssh-dss".

Why this happens

macOS Tahoe 26.x has officially deprecated and disabled the `ssh-dss` (DSA) algorithm because it is considered insecure by modern standards. However, many older routers, switches, and servers still require it.

Fix 1: Manual Flag Override (Free)

You can force the SSH client to allow the old algorithm for a single connection.

**Open Terminal**

Go to Applications > Utilities > Terminal.

**Run with Options**

Type: `ssh -oHostKeyAlgorithms=+ssh-dss user@server-ip`

*Note: Replace `user@server-ip` with your actual login.*

Fix 2: Permanent Config Fix (Free)

If you connect to this server often, you can add it to your SSH config file.

**Open SSH Config**

In Terminal, type: `nano ~/.ssh/config`

**Add Host Entry**

Paste the following block:

```text Host your-server-nickname HostName 192.168.1.1 HostKeyAlgorithms +ssh-dss ```

**Save**

Press `Ctrl + O`, then `Enter`, then `Ctrl + X`.

Fix 3: The Professional Network Toolkit

When managing legacy hardware requires more than just SSH. Working with older systems often means dealing with outdated protocols like FTP or Telnet, which Tahoe is also phasing out.

Recommended Tool: CleanMyMac X

- **Network Optimization:** While not an SSH client, CleanMyMac X can flush the DNS cache and reset network routing tables that often get "tangled" when switching between modern and legacy network environments. [Link: Optimize Network Performance with CleanMyMac X]

Alternative: Termius

If you deal with SSH daily, Termius handles these algorithm incompatibilities automatically with a much better UI than Terminal. [Link: Get Termius for macOS]