The irc_msg_who function in msgs.c in the IRC protocol plugin in libpurple 2.8.0 through 2.9.0 in Pidgin before 2.10.0 does not properly validate characters in nicknames, which allows user-assisted remote attackers to cause a denial of service (NULL pointer dereference and application crash) via a crafted nickname that is not properly handled in a WHO response.
developer.pidgin.im/viewmtn/revision/diff/5749f9193063800d27bef75c2388f6f9cc2f7f37/with/5c2dba4a7e2e76b76e7f472b88953a4316706d43/libpurple/protocols/irc/msgs.c
developer.pidgin.im/viewmtn/revision/info/5c2dba4a7e2e76b76e7f472b88953a4316706d43
pidgin.im/news/security/?id=53
secunia.com/advisories/45663
secunia.com/advisories/45916
securitytracker.com/id?1025961
www.openwall.com/lists/oss-security/2011/08/20/2
www.openwall.com/lists/oss-security/2011/08/22/2
www.securityfocus.com/bid/49268
bugzilla.redhat.com/show_bug.cgi?id=722939
exchange.xforce.ibmcloud.com/vulnerabilities/69340
oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A18005