According to Samba:
"Unescaped user input parameters are passed as arguments to /bin/sh allowing for
remote command execution."
This could be triggered by a remote user if the server uses the non-default
"username map script" smb.conf option, or via remote file and printer management
scripts with an authenticated user.
These will affect Samba as shipped in Red Hat Enterprise Linux 2.1, 3, 4, 5.
Note the non-default "username map script" option only exists on Enterprise Linux 5
removing embargo, now public
An advisory has been issued which should help the problem
described in this bug report. This report is therefore being
closed with a resolution of ERRATA. For more information
on the solution and/or where to find the updated files,
please follow the link below. You may reopen this bug report
if the solution does not work for you.