The remote host is missing an update to openswan announced via advisory DSA 2374-1.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%202374-1

The information security group at ETH Zurich discovered a denial of service vulnerability in the crypto helper handler of the IKE daemon pluto. More information can be found in the upstream advisory at http://openswan.org/download/CVE-2011-4073/CVE-2011-4073.txt For the oldstable distribution (lenny), this problem has been fixed in version 1:2.4.12+dfsg-1.3+lenny4. For the stable distribution (squeeze), this problem has been fixed in version 1:2.6.28+dfsg-5+squeeze1. For the unstable distribution (sid), this problem has been fixed in version 1:2.6.37-1. We recommend that you upgrade your openswan packages.