The function `read_data()` in security.c in curl before version 7.51.0 is vulnerable to memory double free.
https://www.tenable.com/security/tns-2016-21
https://security.gentoo.org/glsa/201701-47
https://curl.haxx.se/docs/adv_20161102E.html
https://curl.haxx.se/CVE-2016-8619.patch
https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2016-8619
https://access.redhat.com/errata/RHSA-2018:3558
https://access.redhat.com/errata/RHSA-2018:2486
http://www.securitytracker.com/id/1037192
http://www.securityfocus.com/bid/94100
http://www.oracle.com/technetwork/security-advisory/cpuoct2018-4428296.html