The CWebAdminMod::ChanPage function in modules/webadmin.cpp in ZNC before 1.4 allows remote authenticated users to cause a denial of service (NULL pointer dereference and crash) by adding a channel with the same name as an existing channel but without the leading # character, related to a "use-after-delete" error.
https://github.com/znc/znc/issues/528
https://github.com/znc/znc/blob/master/ChangeLog.md
http://www.securityfocus.com/bid/66926
http://www.openwall.com/lists/oss-security/2014/12/18/2
http://www.mandriva.com/security/advisories?name=MDVSA-2015:013