The remote host is missing an update to libssh announced via advisory DSA 2577-1.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%202577-1

Multiple vulnerabilities were discovered in libssh by Florian Weimer and Xi Wang: CVE-2012-4559: multiple double free() flaws CVE-2012-4561: multiple invalid free() flaws CVE-2012-4562: multiple improper overflow checks Those could lead to a denial of service by making an ssh client linked to libssh crash, and maybe even arbitrary code execution. For the stable distribution (squeeze), these problems have been fixed in version 0.4.5-3+squeeze1. For the testing distribution (wheezy), these problems have been fixed in version 0.5.3-1. For the unstable distribution (sid), these problems have been fixed in version 0.5.3-1. We recommend that you upgrade your libssh packages.