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Cisco Bug: CSCtc41585 - SSH fails when IOS receives "Client ver string" before sending its own

Last Modified

Sep 21, 2015

Products (6)

  • Cisco IOS
  • Cisco Catalyst 6500 Series Virtual Switching Supervisor Engine 720 with 10GE uplinks
  • Cisco ME 6524-GS Ethernet Switch
  • Cisco Catalyst 6500 Series Supervisor Engine 32 / MSFC2A
  • Cisco ME 6524-GT Ethernet Switch
  • Cisco Catalyst 6500 Series Supervisor Engine 720 / MSFC3

Known Affected Releases


Description (partial)


Unable to connect to 6500 Switch running 12.2(33)SXI2a using SSH with certain SSH Clients.
Using Twisted Network Frameworks SSH Libraries.


This can happen when the Client sends its "version string" before the IOS Server sent the "server version string". In this case the IOS Server will hang and will not send any further packets.
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Bug Details Include

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