The remote host is missing an update to libvirt announced via advisory DSA 2280-1.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%202280-1

It was discovered that libvirt, a library for interfacing with different virtualization systems, is prone to an integer overflow (CVE-2011-2511). Additionally, the stable version is prone to a denial of service, because its error reporting is not thread-safe (CVE-2011-1486). For the stable distribution (squeeze), these problems have been fixed in version 0.8.3-5+squeeze2. For the oldstable distribution (lenny), this problem has been fixed in version 0.4.6-10+lenny2. For the testing distribution (wheezy), these problems will fixed soon. For the unstable distribution (sid), these problems have been fixed in version 0.9.2-7). We recommend that you upgrade your libvirt packages.