The remote host is missing an update to pidgin announced via advisory DSA 1870-1.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%201870-1

Federico Muttis discovered that libpurple, the shared library that adds support for various instant messaging networks to the pidgin IM client, is vulnerable to a heap-based buffer overflow. This issue exists because of an incomplete fix for CVE-2008-2927 and CVE-2009-1376. An attacker can exploit this by sending two consecutive SLP packets to a victim via MSN. The first packet is used to create an SLP message object with an offset of zero, the second packet then contains a crafted offset which hits the vulnerable code originally fixed in CVE-2008-2927 and CVE-2009-1376 and allows an attacker to execute arbitrary code. Note: Users with the Allow only the users below setting are not vulnerable to this attack. If you can't install the below updates you may want to set this via Tools->Privacy. For the stable distribution (lenny), this problem has been fixed in version 2.4.3-4lenny3. For the testing distribution (squeeze), this problem will be fixed soon. For the unstable distribution (sid), this problem has been fixed in version 2.5.9-1. We recommend that you upgrade your pidgin packages.