Guido Günther uploaded new packages for libvirt which fixed the following security problems:
CVE-2011-2511 Integer overflow in VirDomainGetVcpus
CVE-2011-1486 Non thread safe error reporting
For the squeeze-backports distribution the problems have been fixed in version 0.9.2-7~bpo60+1.
For the lenny-backports distribution the problems have been fixed in version 0.8.3-5+squeeze2~bpo50+2.
For lenny-backports only:
If you don't use pinning (see ) 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.  <http://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