Underflow error in Cyberduck

[Flacoss]

Hello ,

I have recently installed Cyberduck and i am trying to connect to a SFTP share but its not working. (windows computer)
It works if i use Filezilla or WinSCP.

The error message i am getting is : Underflow

And this are the logs i am getting :

2023-05-09 09:45:25,290 [background-8] ERROR net.schmizz.concurrent.Promise - <<kex done>> woke to: net.schmizz.sshj.transport.TransportException: Underflow
2023-05-09 09:45:44,900 [sshj-Reader-transfer.kantar.cloud/192.165.204.181:22-1683618344855] ERROR net.schmizz.sshj.transport.TransportImpl - Dying because - Underflow
net.schmizz.sshj.transport.TransportException: Underflow
                             at net.schmizz.sshj.transport.kex.AbstractDHGex.next(AbstractDHGex.java:65) ~[Cyberduck.Protocols.DLL:?]
                             at net.schmizz.sshj.transport.KeyExchanger.handle(KeyExchanger.java:388) ~[Cyberduck.Protocols.DLL:?]
                             at net.schmizz.sshj.transport.TransportImpl.handle(TransportImpl.java:495) [Cyberduck.Protocols.DLL:?]
                             at net.schmizz.sshj.transport.Decoder.decode(Decoder.java:114) ~[Cyberduck.Protocols.DLL:?]
                             at net.schmizz.sshj.transport.Decoder.received(Decoder.java:200) ~[Cyberduck.Protocols.DLL:?]
                             at net.schmizz.sshj.transport.Reader.run(Reader.java:60) [Cyberduck.Protocols.DLL:?]
Caused by: net.schmizz.sshj.common.Buffer$BufferException: Underflow
                             at net.schmizz.sshj.common.Buffer.ensureAvailable(Buffer.java:137) ~[Cyberduck.Protocols.DLL:?]
                             at net.schmizz.sshj.common.Buffer.readUInt32(Buffer.java:303) ~[Cyberduck.Protocols.DLL:?]
                             at net.schmizz.sshj.common.Buffer.readUInt32AsInt(Buffer.java:297) ~[Cyberduck.Protocols.DLL:?]
                             at net.schmizz.sshj.common.Buffer.readString(Buffer.java:414) ~[Cyberduck.Protocols.DLL:?]
                             at net.schmizz.sshj.common.Buffer.readString(Buffer.java:431) ~[Cyberduck.Protocols.DLL:?]
                             at net.schmizz.sshj.common.Buffer.readPublicKey(Buffer.java:487) ~[Cyberduck.Protocols.DLL:?]
                             at net.schmizz.sshj.transport.kex.AbstractDHGex.parseGexReply(AbstractDHGex.java:73) ~[Cyberduck.Protocols.DLL:?]
                             at net.schmizz.sshj.transport.kex.AbstractDHGex.next(AbstractDHGex.java:60) ~[Cyberduck.Protocols.DLL:?]
                             ... 5 more
2023-05-09 09:45:44,900 [background-11] ERROR net.schmizz.concurrent.Promise - <<kex done>> woke to: net.schmizz.sshj.transport.TransportException: Underflow
2023-05-09 09:46:29,531 [sshj-Reader-transfer.kantar.cloud/192.165.204.181:22-1683618389491] ERROR net.schmizz.sshj.transport.TransportImpl - Dying because - Underflow
net.schmizz.sshj.transport.TransportException: Underflow
                             at net.schmizz.sshj.transport.kex.AbstractDHGex.next(AbstractDHGex.java:65) ~[Cyberduck.Protocols.DLL:?]
                             at net.schmizz.sshj.transport.KeyExchanger.handle(KeyExchanger.java:388) ~[Cyberduck.Protocols.DLL:?]
                             at net.schmizz.sshj.transport.TransportImpl.handle(TransportImpl.java:495) [Cyberduck.Protocols.DLL:?]
                             at net.schmizz.sshj.transport.Decoder.decode(Decoder.java:114) ~[Cyberduck.Protocols.DLL:?]
                             at net.schmizz.sshj.transport.Decoder.received(Decoder.java:200) ~[Cyberduck.Protocols.DLL:?]
                             at net.schmizz.sshj.transport.Reader.run(Reader.java:60) [Cyberduck.Protocols.DLL:?]
Caused by: net.schmizz.sshj.common.Buffer$BufferException: Underflow
                             at net.schmizz.sshj.common.Buffer.ensureAvailable(Buffer.java:137) ~[Cyberduck.Protocols.DLL:?]
                             at net.schmizz.sshj.common.Buffer.readUInt32(Buffer.java:303) ~[Cyberduck.Protocols.DLL:?]
                             at net.schmizz.sshj.common.Buffer.readUInt32AsInt(Buffer.java:297) ~[Cyberduck.Protocols.DLL:?]
                             at net.schmizz.sshj.common.Buffer.readString(Buffer.java:414) ~[Cyberduck.Protocols.DLL:?]
                             at net.schmizz.sshj.common.Buffer.readString(Buffer.java:431) ~[Cyberduck.Protocols.DLL:?]
                             at net.schmizz.sshj.common.Buffer.readPublicKey(Buffer.java:487) ~[Cyberduck.Protocols.DLL:?]
                             at net.schmizz.sshj.transport.kex.AbstractDHGex.parseGexReply(AbstractDHGex.java:73) ~[Cyberduck.Protocols.DLL:?]
                             at net.schmizz.sshj.transport.kex.AbstractDHGex.next(AbstractDHGex.java:60) ~[Cyberduck.Protocols.DLL:?]
                             ... 5 more
2023-05-09 09:46:29,532 [background-14] ERROR net.schmizz.concurrent.Promise - <<kex done>> woke to: net.schmizz.sshj.transport.TransportException: Underflow

Anyone knows that the issue can be?

Best Regards

Luis

[dkocher]

The error suggests an interoperability issue with the SFTP server as we fail to read the public key in the response for the Diffie–Hellman key exchange.

[Flacoss]

Yes , we solved the issue by changing the SSH-KEY to the old one.
This means Cyberduck cant handle strong SSH-KEYs.

[ylangisc]

Can you please share the key parameters that do not work?

[dkocher]

Can you let me know the algorithm used for the key that was not working?

[pswag1]

ecdsa-sha2-nistp256

[pswag1]

Same applies to ec host key (fingerprint). Have to convert a customer's client from CyberDuck to competitive product.