acl.c in Tinyproxy before 1.8.3, when an Allow configuration setting specifies a CIDR block, permits TCP connections from all IP addresses, which makes it easier for remote attackers to hide the origin of web traffic by leveraging the open HTTP proxy server.
https://exchange.xforce.ibmcloud.com/vulnerabilities/67256
https://bugzilla.redhat.com/show_bug.cgi?id=694658
http://www.debian.org/security/2011/dsa-2222
http://secunia.com/advisories/44274
http://openwall.com/lists/oss-security/2011/04/08/3