core/nicklist.c in Irssi before 0.8.15 allows remote attackers to cause a denial of service (NULL pointer dereference and application crash) via vectors related to an attempted fuzzy nick match at the instant that a victim leaves a channel.

Irssi before 0.8.15, when SSL is used, does not verify that the server hostname matches a domain name in the subject's Common Name (CN) field or a Subject Alternative Name field of the X.509 certificate, which allows man-in-the-middle attackers to spoof IRC servers via an arbitrary certificate.

CRLF injection vulnerability in the xmms.bx 1.0 script for BitchX allows user-assisted remote attackers to execute arbitrary IRC commands via CRLF sequences in the name of the song in a .mp3 file.

The DCC ACCEPT command handler in irssi before 0.8.9+0.8.10rc5-0ubuntu4.1 in Ubuntu Linux, and possibly other distributions, allows remote attackers to cause a denial of service (application crash) via certain crafted arguments in a DCC command.