Use-after-free vulnerability in opngreduc.c in OptiPNG Hg and 0.7.x before 0.7.3 might allow remote attackers to execute arbitrary code via unspecified vectors related to "palette reduction."
https://exchange.xforce.ibmcloud.com/vulnerabilities/78743
http://www.securityfocus.com/bid/55566
http://sourceforge.net/news/?group_id=151404