Gerd v. Egidy discovered that the Pluto IKE daemon in strongswan, an IPSec implementation for linux, is prone to a denial of service attack via a malicious packet.
For the oldstable distribution (etch), this problem has been fixed in version 2.8.0+dfsg-1+etch1.
For the stable distribution (lenny), this problem has been fixed in version 4.2.4-5+lenny1.
For the testing distribution (squeeze) and the unstable distribution (sid), this problem will be fixed soon.
We recommend that you upgrade your strongswan packages.
MD5 checksums of the listed files are available in the original advisory.