curl before version 7.52.1 is vulnerable to an uninitialized random in libcurl's internal function that returns a good 32bit random value. Having a weak or virtually non-existent random value makes the operations that use it vulnerable.
https://www.tenable.com/security/tns-2017-04
https://security.gentoo.org/glsa/201701-47
https://curl.haxx.se/docs/adv_20161223.html
https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2016-9594