In Irssi before 1.0.3, when receiving a DCC message without source nick/host, it attempts to dereference a NULL pointer. Thus, remote IRC servers can cause a crash.

In Irssi before 1.0.3, when receiving certain incorrectly quoted DCC files, it tries to find the terminating quote one byte before the allocated memory. Thus, remote attackers might be able to cause a crash.

The netjoin processing in Irssi 1.x before 1.0.2 allows attackers to cause a denial of service (use-after-free) and possibly execute arbitrary code via unspecified vectors.

Irssi 0.8.17 before 0.8.21 allows remote attackers to cause a denial of service (out-of-bounds read and crash) via a crafted ANSI x8 color code.

Irssi 0.8.18 before 0.8.21 allows remote attackers to cause a denial of service (out-of-bounds read and crash) via vectors involving strings that are not UTF8.

The nickcmp function in Irssi before 0.8.21 allows remote attackers to cause a denial of service (NULL pointer dereference and crash) via a message without a nick.

Irssi before 0.8.21 allows remote attackers to cause a denial of service (out-of-bounds read and crash) via a string containing a formatting sequence (%[) without a closing bracket (]).

Use-after-free vulnerability in Irssi before 0.8.21 allows remote attackers to cause a denial of service (crash) via an invalid nick message.

The unformat_24bit_color 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 format_send_to_gui 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.