Linksys WRT54G routers version 5 (running VXWorks) allow remote attackers to cause a denial of service by sending a malformed DCC SEND string to an IRC channel, which causes an IRC connection reset, possibly related to the masquerading code for NAT environments, and as demonstrated via (1) a DCC SEND with a single long argument, or (2) a DCC SEND with IP, port, and filesize arguments with a 0 value.