ssh-action@master fails with RSA key: invalid CRT coefficient

[kangwonchul]

When running a GitHub Actions workflow using appleboy/ssh-action@master, the SSH connection fails with the following error:

2025/12/02 05:42:09 ssh.ParsePrivateKey: crypto/rsa: invalid CRT coefficient
2025/12/02 05:42:10 ssh: handshake failed: ssh: unable to authenticate, attempted methods [none], no supported methods remain
Error: Process completed with exit code 1.

This happened consistently when attempting to connect to an EC2 instance using an RSA private key stored in GitHub Secrets.

Workflow Configuration

Here is the step that caused the failure:

- name: server connect
  uses: appleboy/ssh-action@master
  with:
    host: ${{ secrets.TEST_SERVER_HOST }}
    username: ec2-user
    key: ${{ secrets.PRIVATE_KEY }}
    timeout: 60s
    port: 22

Once I downgraded to: appleboy/ssh-action@v1.2.3 the problem was resolved.