NetHack is a single player dungeon exploration game. Starting with version 3.6.2 and prior to version 3.6.7, illegal input to the "C" (call) command can cause a buffer overflow and crash the NetHack process. This vulnerability may be a security issue for systems that have NetHack installed suid/sgid and for shared systems. For all systems, it may result in a process crash. This issue is resolved in NetHack 3.6.7. There are no known workarounds.
Please bump to 3.6.7.