Summary: A Fix for a Cisco ASA firewall when you can't login over SSH.
Date: Around 2007
Refactor: 16 January 2025: Checked links and formatting.

Symptom: Unable to establish a SSH session with a Cisco ASA firewall. After logging in using ASDM you see this error in the log:

fail to establish SSH session because RSA host key retrieval failed

To fix, go to the command line interface:

ASDM → Tools → Command Line Interface

And enter these commands:

conf t
crypto key generate rsa general-keys modulus 1024

Now you can establish a connection over SSH.