The remote host is missing an update to acpid announced via advisory DSA 1786-1.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%201786-1

It was discovered that acpid, a daemon for delivering ACPI events, is prone to a denial of service attack by opening a large number of UNIX sockets, which are not closed properly. For the stable distribution (lenny), this problem has been fixed in version 1.0.8-1lenny1. For the oldstable distribution (etch), this problem has been fixed in version 1.0.4-5etch1. For the testing distribution (squeeze) and the unstable distribution (sid), this problem has been fixed in version 1.0.10-1. We recommend that you upgrade your acpid packages.