Apple has released a security update for Mac OS X 10.2.6 client and server installations.
The company says it "addresses a potential security issue when the Apple filing protocol (AFP) is used to reshare a Network File System (NFS) mount. This update also addresses a situation where LDAP bind authentication requests may be improperly sent when using Kerberos authentication."
The 4.5MB update - 2003-06-09 - is available for download from the Apple site. Alternatively, you can use OS X's Software Update System Preference.