SGI has posted a new tardist for Samba 2.2.8a on their Beta Freeware site. This release addresses a security concern which can lead to an anonymous user gaining root access on a Samba serving system. All versions of Samba up to and including Samba 2.2.8 are vulnerable. An active exploit of the bug has been reported in the wild, so if you use Samba you should upgrade immediately.
More information can be found on the Samba.org web site.