The default configuration for cURL and libcurl before 7.42.1 sends custom HTTP headers to both the proxy and destination server, which might allow remote proxy servers to obtain sensitive information by reading the header contents.
http://kb.juniper.net/InfoCenter/index?page=content&id=JSA10743
http://lists.apple.com/archives/security-announce/2015/Aug/msg00001.html
http://lists.opensuse.org/opensuse-updates/2015-05/msg00017.html
https://kc.mcafee.com/corporate/index?page=content&id=SB10131
https://support.apple.com/kb/HT205031
http://www.debian.org/security/2015/dsa-3240
http://www.oracle.com/technetwork/security-advisory/cpuoct2018-4428296.html
http://www.oracle.com/technetwork/topics/security/bulletinjan2016-2867206.html
http://www.oracle.com/technetwork/topics/security/cpujan2016-2367955.html
http://www.oracle.com/technetwork/topics/security/cpuoct2015-2367953.html