The Samba Team reports:
Secunia Research reported a vulnerability that allows for the execution of arbitrary code in nmbd. This defect may only be exploited when the "wins support" parameter has been enabled in smb.conf.
Samba developers have discovered what is believed to be a non-exploitable buffer over in nmbd during the processing of GETDC logon server requests. This code is only used when the Samba server is configured as a Primary or Backup Domain Controller.