curl before version 7.51.0 doesn't parse the authority component of the URL correctly when the host name part ends with a '#' character, and could instead be tricked into connecting to a different host. This may have security implications if you for example use an URL parser that follows the RFC to check for allowed domains before using curl to request them.
https://www.tenable.com/security/tns-2016-21
https://security.gentoo.org/glsa/201701-47
https://curl.haxx.se/docs/adv_20161102J.html
https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2016-8624
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/94103
http://www.oracle.com/technetwork/security-advisory/cpuoct2018-4428296.html