The remote Debian host is missing a security-related update.
A stack overflow vulnerability was discovered within the gdImageFillToBorder function in libgd2, a library for programmatic graphics creation and manipulation, triggered when invalid colors are used with truecolor images. A remote attacker can take advantage of this flaw to cause a denial-of-service against an application using the libgd2 library.
Upgrade the libgd2 packages. For the stable distribution (jessie), this problem has been fixed in version 2.1.0-5+deb8u8.