Ircd hybrid-6 (up to beta 58) has a vulnerability which can allow remote access to the irc server (ircd). In most cases this attack results in the attacker gaining the privileges of the user 'irc'.
This vulnerability is in the invite handling code (m_invite). In a channel with operators (ops) and modes +pi (paranoid + invite-only), a channel invitation is reported to all other operators. The buffer used to store the invitation notice can be overflown by up to 15 bytes.