mystring.c in hybserv in IRCD-Hybrid (aka Hybrid2 IRC Services) 1.9.2 through 1.9.4 allows remote attackers to cause a denial of service (daemon crash) via a ":help \t" private message to the MemoServ service.
Improper Input Validation The product receives input or data, but it does
not validate or incorrectly validates that the input has the
properties that are required to process the data safely and
correctly.