The remote host is missing an update to libapache2-mod-authnz-external announced via advisory DSA 2279-1.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%202279-1

It was discovered that libapache2-mod-authnz-external, an apache authentication module, is prone to an SQL injection via the $user paramter. For the stable distribution (squeeze), this problem has been fixed in version 3.2.4-2+squeeze1. The oldstable distribution (lenny) does not contain libapache2-mod-authnz-external For the testing distribution (wheezy), this problem will be fixed soon. For the unstable distribution (sid), this problem has been fixed in version 3.2.4-2.1. We recommend that you upgrade your libapache2-mod-authnz-external packages.