The remote host is missing an update to opensaml2, shibboleth-sp2 announced via advisory DSA 1895-2.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%201895-2

In DSA-1895-1, the xmltooling package was updated to address several security issues. It turns out that the change related to SAML metadata processing for key constraints caused problems when applied without the matching changes in the opensaml2 and shibboleth-sp2 packages. For the stable distribution (lenny), this problem has been fixed in version 2.0-2+lenny1 of the opensaml2 packages, and version 2.0.dfsg1-4+lenny1 of the shibboleth-sp2 packages. We recommend that you upgrade your opensaml2 and shibboleth-sp2