Debian DSA-1750-1 High Severity Libpng Denial Of Service Issue

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...