The nss_dns implementation of getnetbyname in GNU C Library (aka glibc) before 2.21, when the DNS backend in the Name Service Switch configuration is enabled, allows remote attackers to cause a denial of service (infinite loop) by sending a positive answer while a network name is being process.
http://www.openwall.com/lists/oss-security/2014/12/18/1
http://lists.opensuse.org/opensuse-updates/2015-02/msg00089.html
https://sourceware.org/bugzilla/show_bug.cgi?id=17630
http://www.ubuntu.com/usn/USN-2519-1
http://www.securityfocus.com/bid/71670
https://security.gentoo.org/glsa/201602-02
http://www.oracle.com/technetwork/security-advisory/cpujan2018-3236628.html
https://access.redhat.com/errata/RHSA-2018:0805
http://seclists.org/fulldisclosure/2019/Jun/18
https://seclists.org/bugtraq/2019/Jun/14
http://seclists.org/fulldisclosure/2019/Sep/7