The remote host is missing an update to strongswan announced via advisory DSA 1899-1.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%201899-1

Several remote vulnerabilities have been discovered in strongswan, an implementation of the IPSEC and IKE protocols. The Common Vulnerabilities and Exposures project identifies the following problems: CVE-2009-1957 CVE-2009-1958 The charon daemon can crash when processing certain crafted IKEv2 packets. (The old stable distribution (etch) was not affected by these two problems because it lacks IKEv2 support.) CVE-2009-2185 CVE-2009-2661 The pluto daemon could crash when processing a crafted X.509 certificate. For the old stable distribution (etch), these problems have been fixed in version 2.8.0+dfsg-1+etch2. For the stable distribution (lenny), these problems have been fixed in version 4.2.4-5+lenny3. For the unstable distribution (sid), these problems have been fixed in version 4.3.2-1.1. We recommend that you upgrade your strongswan packages.