How to fix broken SSH on Synology DSM (no matching cipher found)
Whilst trying to log-in to my Synology DS414 NAS today via SSH I was greeted with this error:
Unable to negotiate with 192.168.0.xxx port xxx: no matching cipher found. Their offer: aes128-cbc,3des-cbc,aes192-cbc,aes256-cbc
I am running DSM version 6.2.2-24922 Update 4 (although 6.2.3-25426 is available as an update).
It would appear that since I last attempted to log in, Synology have changed their security settings.
To fix this I found a helpful blog post by Mattias Geniar.
His solution that worked for me was to go to Control Panel in Synology DSM, then choose from the left-hand column “Terminal & SNMP” > “Terminal”, and then go into “Advanced Settings” and change the value to “High”.
After applying the setting SSH is back working again with no errors.
Screenshots below:
Let me know if this works for you too. Thanks Mattias for the tip!
Related links: