Incoming packet was garbled on decryption using Winscp

WinSCP is a free SFTP client and FTP client for Microsoft Windows. You can use it to copy files between a local computer and remote servers using FTP, FTPS, SCP, SFTP, WebDAV or S3 file transfer protocols. In a recent project I was using it to transfer a number of VMs between old and new infrastructure where storage vmotion wasn’t an option. Having done a half dozen larger vms already I was a little surprised to get the message “Incoming packet was garbled on decryption”

According to the support website

This error occurs when WinSCP decrypts an SSH packet and the decrypted data makes no sense. This probably means something has gone wrong in the encryption or decryption process. It’s difficult to tell from this error message whether the problem is in the client or in the server, or in between.

You can try enabling Miscomputes SSH-2 encryption keys or Ignores SSH-2 maximum packet size session option.

Sometimes the error is a result of the connection fatally failing for whatever reason even completely unrelated to the encryption. For example, when the server runs out of disk space.



When I read the last item – I went back to check that the vm was in fact the size I had been given – and discovered that it contained a much larger disk than anticipated. The application hadn’t looked to see if the available space matched what was to be copied !!

Aborting the transfer – clearing back the space and selecting an alternative datastore  – the transfer proceeded as expected !

I also noted that the new version of Winscp 5.17 – just released  is a major application update. New features and enhancements include:

  • Improvements to sessions and workspace management, so that WinSCP can now easily restore tabs that were open when it was last closed.
  • Hardware-accelerated AES.
  • Extension Archive and Download to archive remote files and download the archive.
  • Improvements to Synchronization checklist window.
  • Allowed sorting of find results.
  • SSH core upgraded to PuTTY 0.73.
  • The binaries are signed with new EV certificate valid until February 2023.