The png_check_keyword function in pngwutil.c in libpng before 1.0.42, and 1.2.x before 1.2.34, 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, related to an implicit cast of the '\0' character constant to a NULL pointer. NOTE: some sources incorrectly report this as a double free vulnerability.
https://exchange.xforce.ibmcloud.com/vulnerabilities/48128
http://www.mandriva.com/security/advisories?name=MDVSA-2009:051
http://www.debian.org/security/2009/dsa-1750
http://security.gentoo.org/glsa/glsa-200903-28.xml
http://secunia.com/advisories/34388
http://secunia.com/advisories/34320
http://openwall.com/lists/oss-security/2009/01/09/1
http://lists.opensuse.org/opensuse-security-announce/2009-02/msg00000.html