SSH used to work but failed after system updated
Applicable Products
QTS 5.2.0 and later
Scenario
After updating your NAS device to firmware version QTS 5.2.0_20240711, you may encounter issues when attempting to connect via SSH or SFTP using clients such as MobaXterm. A common error message may read:
Couldn't agree a host key algorithm (available: rsa-sha2-512, rsa-sha2-256).This issue arises due to security enhancements introduced in QTS 5.2.0, specifically updates to the OpenSSH protocol for better compliance with modern encryption standards. The system now uses OpenSSH 9.8p1, which discontinues support for certain older algorithms.
Workaround
1. Update Your SSH Client
Download the latest version of MobaXterm from the official website.
Install or reinstall the updated version on your system.
Attempt to connect to the NAS device again via SSH or SFTP.
2. Consider Using Alternative SSH Clients
If the issue persists, you may try using other up-to-date SSH clients that support the latest OpenSSH standards, such as:
PuTTY (latest version)
Windows Terminal (with updated OpenSSH support)
3. For Mobile Users (e.g., nPlayer)
Some mobile applications may not yet support the enhanced encryption protocols. In such cases, we recommend either:
Contacting the app developer for information on upcoming support for the new standards, or
Trying alternative mobile apps that offer compatibility with the latest OpenSSH protocols.
