Libreswan 3.6 allows remote attackers to cause a denial of service (crash) via a small length value and (1) no version or (2) an invalid major number in an IKE packet.
lists.fedoraproject.org/pipermail/package-announce/2013-December/124911.html
lists.fedoraproject.org/pipermail/package-announce/2013-December/124928.html
lists.fedoraproject.org/pipermail/package-announce/2013-December/124943.html
secunia.com/advisories/56276
libreswan.org/security/CVE-2013-4564/CVE-2013-4564.txt.asc
lists.libreswan.org/pipermail/swan-announce/2013/000007.html