The g_markup_escape_text function in the SILC protocol plug-in in libpurple 2.10.0 and earlier, as used in Pidgin and possibly other products, allows remote attackers to cause a denial of service (crash) via invalid UTF-8 sequences that trigger use of invalid pointers and an out-of-bounds read, related to interactions with certain versions of glib2.

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.

directconn.c in the MSN protocol plugin in libpurple 2.7.6 through 2.7.8 in Pidgin before 2.7.9 allows remote authenticated users to cause a denial of service (NULL pointer dereference and application crash) via a short p2pv2 packet in a DirectConnect (aka direct connection) session.

The XMPP protocol plugin in libpurple in Pidgin before 2.6.2 does not properly handle an error IQ stanza during an attempted fetch of a custom smiley, which allows remote attackers to cause a denial of service (application crash) via XHTML-IM content with cid: images.

libpurple/protocols/irc/msgs.c in the IRC protocol plugin in libpurple in Pidgin before 2.6.2 allows remote IRC servers to cause a denial of service (NULL pointer dereference and application crash) via a TOPIC message that lacks a topic string.

The msn_slp_sip_recv function in libpurple/protocols/msn/slp.c in the MSN protocol plugin in libpurple in Pidgin before 2.6.2 allows remote attackers to cause a denial of service (NULL pointer dereference and application crash) via an SLP invite message that lacks certain required fields, as demonstrated by a malformed message from a KMess client.

The msn_slp_process_msg function in libpurple/protocols/msn/slpcall.c in the MSN protocol plugin in libpurple 2.6.0 and 2.6.1, as used in Pidgin before 2.6.2, allows remote attackers to cause a denial of service (application crash) via a handwritten (aka Ink) message, related to an uninitialized variable and the incorrect "UTF16-LE" charset name.