The send_dg function in resolv/res_send.c in GNU C Library (aka glibc or libc6) before 2.20 does not properly reuse file descriptors, which allows remote attackers to send DNS queries to unintended locations via a large number of requests that trigger a call to the getaddrinfo function.
https://sourceware.org/bugzilla/show_bug.cgi?id=15946
https://security.gentoo.org/glsa/201602-02
https://github.com/golang/go/issues/6336
https://access.redhat.com/errata/RHSA-2016:1207
http://www.ubuntu.com/usn/USN-2519-1
http://www.securityfocus.com/bid/72844
http://www.openwall.com/lists/oss-security/2015/01/28/20
http://seclists.org/fulldisclosure/2021/Sep/0
http://rhn.redhat.com/errata/RHSA-2015-0863.html
http://lists.opensuse.org/opensuse-updates/2015-02/msg00089.html