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.
curl.haxx.se/docs/adv_20150429.html
kb.juniper.net/InfoCenter/index?page=content&id=JSA10743
lists.apple.com/archives/security-announce/2015/Aug/msg00001.html
lists.opensuse.org/opensuse-updates/2015-05/msg00017.html
www.debian.org/security/2015/dsa-3240
www.oracle.com/technetwork/security-advisory/cpuoct2018-4428296.html
www.oracle.com/technetwork/topics/security/bulletinjan2016-2867206.html
www.oracle.com/technetwork/topics/security/cpujan2016-2367955.html
www.oracle.com/technetwork/topics/security/cpuoct2015-2367953.html
www.securityfocus.com/bid/74408
www.securitytracker.com/id/1032233
www.ubuntu.com/usn/USN-2591-1
kc.mcafee.com/corporate/index?page=content&id=SB10131
support.apple.com/kb/HT205031