The remote host is missing an update to libpng announced via advisory DSA 1750-1.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%201750-1

Several vulnerabilities have been discovered in libpng, a library for reading and writing PNG files. The Common Vulnerabilities and Exposures project identifies the following problems: The png_handle_tRNS function allows attackers to cause a denial of service (application crash) via a grayscale PNG image with a bad tRNS chunk CRC value. (CVE-2007-2445) Certain chunk handlers allow attackers to cause a denial of service (crash) via crafted pCAL, sCAL, tEXt, iTXt, and ztXT chunking in PNG images, which trigger out-of-bounds read operations. (CVE-2007-5269) libpng allows context-dependent attackers to cause a denial of service (crash) and possibly execute arbitrary code via a PNG file with zero length unknown chunks, which trigger an access of uninitialized memory. (CVE-2008-1382) The png_check_keyword might allow context-dependent attackers to set the value of an arbitrary memory location to zero via vectors involving creation of crafted PNG files with keywords. (CVE-2008-5907) A memory leak in the png_handle_tEXt function allows context-dependent attackers to cause a denial of service (memory exhaustion) via a crafted PNG file. (CVE-2008-6218) libpng allows context-dependent attackers to cause a denial of service (application crash) or possibly execute arbitrary code via a crafted PNG file that triggers a free of an uninitialized pointer in (1) the png_read_png function, (2) pCAL chunk handling, or (3) setup of 16-bit gamma tables. (CVE-2009-0040) For the old stable distribution (etch), these problems have been fixed in version1.2.15~beta5-1+etch2. For the stable distribution (lenny), these problems have been fixed in version 1.2.27-2+lenny2. (Only CVE-2008-5907, CVE-2008-5907 and CVE-2009-0040 affect the stable distribution.) For the unstable distribution (sid), these problems have been fixed in version 1.2.35-1. We recommend that you upgrade your libpng packages.