The remote Debian host is missing a security-related update.
Several vulnerabilities were discovered in libgd2, a library for programmatic graphics creation and manipulation. A remote attacker can take advantage of these flaws to cause a denial-of-service against an application using the libgd2 library.
Upgrade the libgd2 packages. For the stable distribution (jessie), these problems have been fixed in version 2.1.0-5+deb8u3.