SFTPGo: Denial of service via malformed SSH channel request

Summary

A flaw in the SSH service allows an authenticated client to crash the server by sending a malformed protocol message while opening a channel.

Impact

Any user able to authenticate over SSH can trigger an unhandled error condition that aborts the server process. This results in a denial of service affecting all connected users until the service is restarted. No confidentiality or integrity impact has been identified; the issue is limited to availability.