If you're using Samba for Linux and Windows interoperability then you should upgrade to version 3.0.25. The new version, released May 16, fixes three security problems.
There are two remote code execution vulnerabilities and one privilege escalation vulnerability.
There are also several new features and enhancements. For example, Samba now has support for secure DDNS updates as part of the 'net ads join' process, and support for passing Windows security descriptors to a VFS plug-in that allows multiple Unix ACL implements to run side by side on the same server.