This indicates an attack attempt against an Unauthorized Access vulnerability in Samba server.
The vulnerability is caused by a lack of sanitization in the "share name" when registry shares are enabled. By sending a specially crafted "TREE_CONNECT_ANDX" request to a samba server, a remote attacker can access the root file system.
Samba 3.2.0 through 3.2.6
Security Bypass: Remote attackers can bypass the security checking of vulnerable systems.
Refer to the vendor's web site for suggested workground.