The SMB2_tcon function in fs/cifs/smb2pdu.c in the Linux kernel before 3.16.3 allows remote CIFS servers to cause a denial of service (NULL pointer dereference and client system crash) or possibly have unspecified other impact by deleting the IPC$ share during resolution of DFS referrals.
https://github.com/torvalds/linux/commit/18f39e7be0121317550d03e267e3ebd4dbfbb3ce
http://www.ubuntu.com/usn/USN-2394-1
http://www.securityfocus.com/bid/69867
http://www.openwall.com/lists/oss-security/2014/09/22/4
http://www.kernel.org/pub/linux/kernel/v3.x/ChangeLog-3.16.3