The remote Debian host is missing a security-related update.
Hans Jerry Illikainen discovered that libgd2, a library for programmatic graphics creation and manipulation, suffers of a signedness vulnerability which may result in a heap overflow when processing specially crafted compressed gd2 data. A remote attacker can take advantage of this flaw to cause an application using the libgd2 library to crash, or potentially, to execute arbitrary code with the privileges of the user running the application.
Upgrade the libgd2 packages. For the oldstable distribution (wheezy), this problem has been fixed in version 2.0.36~rc1~dfsg-6.1+deb7u2. For the stable distribution (jessie), this problem has been fixed in version 2.1.0-5+deb8u1.