The Samba Team reports:
Internally Samba's file server daemon, smbd, implements support for deferred file open calls in an attempt to serve client requests that would otherwise fail due to a share mode violation. When renaming a file under certain circumstances it is possible that the request is never removed from the deferred open queue. smbd will then become stuck is a loop trying to service the open request. This bug may allow an authenticated user to exhaust resources such as memory and CPU on the server by opening multiple CIFS sessions, each of which will normally spawn a new smbd process, and sending each connection into an infinite loop.