The remote host is missing an update to qemu-kvm announced via advisory DSA 2270-1.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%202270-1

It was discovered that incorrect sanitising of virtio queue commands in KVM, a solution for full virtualization on x86 hardware, could lead to denial of service of the execution of arbitrary code. The oldstable distribution (lenny) is not affected by this problem. For the stable distribution (squeeze), this problem has been fixed in version 0.12.5+dfsg-5+squeeze4. For the unstable distribution (sid), this problem has been fixed in version 0.14.1+dfsg-2. We recommend that you upgrade your qemu-kvm packages.