ZNC 1.8.0 up to 1.8.1-rc1 allows authenticated users to trigger an application crash (with a NULL pointer dereference) if echo-message is not enabled and there is no network.
https://github.com/znc/znc/commit/d229761821da38d984a9e4098ad96842490dc001
https://github.com/znc/znc/commit/2390ad111bde16a78c98ac44572090b33c3bd2d8