libcurl is vulnerable to a cookie leak vulnerability when doing requests across domains with matching tails.
When communicating over HTTP(S) and having libcurl's cookie engine enabled, libcurl stores and holds cookies for use when subsequent requests are done to hosts and paths that match those kept cookies. Due to a bug in the tailmatching function, libcurl could wrongly send cookies meant for the domain 'ample.com' when communicating with 'example.com'.
This vulnerability can be used to hijack sessions in targeted attacks since registering domains using a known domain's name as an ending is trivial.
Both curl the command line tool and applications using the libcurl library are vulnerable.