IRC Xchat client versions 1.4.2 and earlier allows remote attackers to execute arbitrary commands by encoding shell metacharacters into a URL which XChat uses to launch a web browser.

Format string vulnerability in XChat 1.2.x allows remote attackers to execute arbitrary code via a malformed nickname.

XChat 1.8.7 and earlier, including default configurations of 1.4.2 and 1.4.3, allows remote attackers to execute arbitrary IRC commands as other clients via encoded characters in a PRIVMSG command that calls CTCP PING, which expands the characters in the client response when the percascii variable is set.

XChat IRC client allows remote attackers to execute arbitrary commands via a /dns command on a host whose DNS reverse lookup contains shell metacharacters.

xchat 2.0.6 allows remote attackers to cause a denial of service (crash) via a passive DCC request with an invalid ID number, which causes a null dereference.

Stack-based buffer overflow in the Socks-5 proxy code for XChat 1.8.0 to 2.0.8, with socks5 traversal enabled, allows remote attackers to execute arbitrary code.

Unspecified vulnerability in Xchat 2.6.7 and earlier allows remote attackers to cause a denial of service (crash) via unspecified vectors involving the PRIVMSG command. NOTE: the vendor has disputed this vulnerability, stating that it does not affect 2.6.7 "or any recent version"

The ssl_do_connect function in common/server.c in HexChat before 2.10.2, XChat, and XChat-GNOME does not verify that the server hostname matches a domain name in the X.509 certificate, which allows man-in-the-middle attackers to spoof SSL servers via an arbitrary valid certificate.