Christian Perrier uploaded new packages for samba which fixed the
following security problems:

  A vulnerability has been discovered in samba, a SMB/CIFS file,
  print, and login server for Unix.

  The sid_parse() function does not correctly check its input lengths
  when reading a binary representation of a Windows SID (Security ID).
  This allows a malicious client to send a sid that can overflow the
  stack variable that is being used to store the SID in the Samba smbd

For the lenny-backports distribution the problems have been fixed in
version 2:3.5.5~dfsg-1~bpo50+1.

Upgrade instructions

If you don't use pinning (see [1]) you have to update the package
manually via "apt-get -t lenny-backports install <packagelist>" with
the packagelist of your installed packages affected by this update.
[1] <>

We recommend to pin the backports repository to 200 so that new
versions of installed  backports will be installed automatically.

  Package: *
  Pin: release a=lenny-backports
  Pin-Priority: 200