Software⏱️ 4 min read📅 2026-06-11

How to Fix: warning message "kex protocol error: type 7" during scp, rsync or shell work

Gentoo Linux OpenSSH configuration issue causing kex protocol errors during SCP, Rsync, or shell work.

Quick Answer: Check OpenSSH configuration files for any custom settings that may be causing the issue and adjust them to default values if necessary.

📋 Table of Contents

  1. 💡 Why You Are Getting This Error
  2. ✅ Best Solutions to Fix It
  3. 💡 Conclusion

Warning messages indicating 'kex protocol error: type 7' during SCP, RSync, or shell work on a Gentoo Linux server are causing frustration for users. These errors occur in proportion to traffic and can be triggered by both the server (running OpenSSH_7.2p2 and OpenSSL 1.0.2h) and clients (including notebooks with the same SSH client version as the server, or Qnap NAS devices using a different SSH client version). Despite these warnings, file transfers seem to work without issues, but the error messages clutter the screen output.

Eliminating these warning messages is crucial for maintaining a clean and efficient remote access experience. This guide aims to help troubleshoot and resolve 'kex protocol error: type 7' during SCP, RSync, or shell work on Gentoo Linux servers.

💡 Why You Are Getting This Error

  • The primary cause of 'kex protocol error: type 7' is likely related to the OpenSSH version used by both the server and clients. The kex protocol (Key Exchange) is a standard mechanism for securely exchanging cryptographic keys between two parties. Type 7 refers to the Diffie-Hellman key exchange algorithm, which might be incompatible or insecure with newer versions of OpenSSL. This incompatibility can lead to authentication failures and 'kex protocol error: type 7' warnings.
  • An alternative reason could be related to the specific SSH client implementation used by Qnap NAS devices. Although they use OpenSSH_7.2p2, a different version of OpenSSL (1.0.1t) might introduce compatibility issues with the server's OpenSSH client.

✅ Best Solutions to Fix It

Enabling TLSv1.3 and Updating SSH Client Versions

  1. Step 1: Update both the server and clients to use a compatible version of OpenSSL, preferably 1.0.2h or later. This will ensure that the kex protocol is used with a secure Diffie-Hellman key exchange algorithm.
  2. Step 2: Enable TLSv1.3 on the OpenSSH server by adding the following configuration option: `ProtocolVersion 1.5`. Restart the SSH service to apply the changes.
  3. Step 3: Update the SSH client versions on both the notebook and Qnap NAS devices to match or exceed the version used on the server (OpenSSH_7.2p2). This will ensure that the kex protocol is used with a compatible Diffie-Hellman key exchange algorithm.

Disabling KEXALG and Using a Different Key Exchange Algorithm

  1. Step 1: On the server, add the following configuration option to disable kexalgs (KEX algorithms): `KexAlgorithms +ssh-dss`. This will force the use of a different key exchange algorithm, such as SSH-DSS. Restart the SSH service to apply the changes.
  2. Step 2: Note: Disabling KEXALG might reduce the security of the SSH connection. It is recommended to update the OpenSSL version instead.

💡 Conclusion

By following these steps, users can resolve 'kex protocol error: type 7' warnings during SCP, RSync, or shell work on Gentoo Linux servers. Enabling TLSv1.3 and updating SSH client versions is a primary fix method, while disabling KEXALG and using a different key exchange algorithm are alternative solutions to consider.

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