Peter Samuelson uploaded new packages for subversion which fixed the
following security problems:

CVE-2011-1752
  Subversion's mod_dav_svn Apache HTTPD server module will dereference
  a NULL pointer if asked to deliver baselined WebDAV resources.
  http://subversion.apache.org/security/CVE-2011-1752-advisory.txt

CVE-2011-1783
  Subversion's mod_dav_svn Apache HTTPD server module may in certain
  scenarios enter a logic loop which does not exit and which allocates
  memory in each iteration, ultimately exhausting all the available
  memory on the server.
  http://subversion.apache.org/security/CVE-2011-1783-advisory.txt

CVE-2011-1921
  Subversion's mod_dav_svn Apache HTTPD server module may leak to
  remote users the file contents of files configured to be unreadable
  by those users.
  http://subversion.apache.org/security/CVE-2011-1921-advisory.txt

For the lenny-backports distribution the problems have been fixed in
version 1.6.12dfsg-6~bpo50+1.

For the stable distribution (squeeze) the problems have been fixed in
version 1.6.12dfsg-6 [stable-sec].

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] <https://backports.debian.org/Instructions>

We recommend to pin (in /etc/apt/preferences) 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