An issue was discovered in Irssi before 1.0.4. When receiving messages with invalid time stamps, Irssi would try to dereference a NULL pointer.

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 buf.pl script before 2.20 in Irssi before 0.8.20 uses weak permissions for the scrollbuffer dump file created between upgrades, which might allow local users to obtain sensitive information from private chat conversations by reading the file.