Openswan 2.6.29 through 2.6.35 allows remote attackers to cause a denial of service (NULL pointer dereference and pluto IKE daemon crash) via an ISAKMP message with an invalid KEY_LENGTH attribute, which is not properly handled by the error handling function.
http://www.redhat.com/support/errata/RHSA-2011-1356.html
http://www.openswan.org/download/CVE-2011-3380/CVE-2011-3380.txt