Irssi 1.3.x and 1.4.x before 1.4.4 has a use-after-free because of use of a stale special collector reference. This occurs when printing of a non-formatted line is concurrent with printing of a formatted line.

The formatsendtogui function in the format parsing code in Irssi before 0.8.20 allows remote attackers to cause a denial of service (heap corruption and crash) via vectors involving the length of a string.

The unformat24bitcolor function in the format parsing code in Irssi before 0.8.20, when compiled with true-color enabled, allows remote attackers to cause a denial of service (heap corruption and crash) via an incomplete 24bit color code.

The official irssi docker images before 1.1-alpine (Alpine specific) contain a blank password for a root user. System using the irssi docker container deployed by affected versions of the Docker image may allow an remote attacker to achieve root access with a blank password.