The (1) Conn_StartLogin and (2) cb_Read_Resolver_Result functions in conn.c in ngIRCd 18 through 20.2, when the configuration option NoticeAuth is enabled, does not properly handle the return code for the Handle_Write function, which allows remote attackers to cause a denial of service (assertion failure and server crash) via unspecified vectors, related to a "notice auth" message not being sent to a new client.
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.