Unfortunately the issue has been made public by the publishing of the patch. Which is now committed upstream and tagged as the fix for CVE-2013-4297, but the CVE hasn't actually been published yet. Since the fix is out there might as well get it in Gentoo and stabilized.
target keywords: amd64 x86
Waiting for CVE to be published to decide whether to GLSA.
 indicates that this is a DoS (invalid free) vuln.
The virFileNBDDeviceAssociate function in util/virfile.c in libvirt 1.1.2
and earlier allows remote authenticated users to cause a denial of service
(uninitialized pointer dereference and crash) via unspecified vectors.
Added to existing GLSA draft
This issue was resolved and addressed in
GLSA 201412-04 at http://security.gentoo.org/glsa/glsa-201412-04.xml
by GLSA coordinator Kristian Fiskerstrand (K_F).