The user followed the solution from JSA76462 [juniper.net] because his scanner was detecting the vulnerability CVE-2023-48795. Now, SSH is not working.

Solution from JSA76462 [juniper.net]:

This issue can be completely remediated by excluding the chacha20-poly1305 cipher from SSH and configuring the following ciphers for SSH:

user@junos# set system services ssh ciphers [[email protected] [email protected]]

• SSH is no longer working.
• User is using the latest Putty version.
• If user removes that configuration line, SSH through Putty works again.

Some SSH clients like Putty are a little old and might not include some of the newest and more secure ciphers.

Putty for instance doesn't include those ciphers that we are configuring aes128-gcm and aes256-gcm, that is why SSH stopped working, because the SSH connection would not establish due to the cipher mismatch.

And when you apply the solution, you are limiting SSH connections to only these two more secure ciphers (which are not included in Putty):

The solution is to use another SSH client that includes these more secure ciphers. For instance, this is a screenshot from Bitvise:

Make sure to check your SSH client and confirm if it supports those ciphers mentioned in the JSA.