The remote Debian host is missing a security-related update.
Several vulnerabilities were discovered in libxml2, a library providing support to read, modify and write XML and HTML files. A remote attacker could provide a specially crafted XML or HTML file that, when processed by an application using libxml2, would cause a denial-of-service against the application, or potentially the execution of arbitrary code with the privileges of the user running the application.
Upgrade the libxml2 packages. For the stable distribution (jessie), these problems have been fixed in version 2.9.1+dfsg1-5+deb8u2.