Format string vulnerability in the -a option (daemon mode) in Proxytunnel before 1.2.3 allows remote attackers to execute arbitrary code via format string specifiers in an invalid proxy answer.
https://exchange.xforce.ibmcloud.com/vulnerabilities/17945
https://euvd.enisa.europa.eu/vulnerability/EUVD-2004-0990
http://www.securityfocus.com/bid/11592