Samba 4.x before 4.0.4, when configured as an Active Directory domain controller, uses world-writable permissions on non-default CIFS shares, which allows remote authenticated users to read, modify, create, or delete arbitrary files via standard filesystem operations.
http://www.samba.org/samba/security/CVE-2013-1863
http://www.samba.org/samba/ftp/patches/security/samba-4.0.3-CVE-2013-1863.patch