libymsg.c in the Yahoo! protocol plugin in libpurple in Pidgin 2.6.0 through 2.7.10 allows (1) remote authenticated users to cause a denial of service (NULL pointer dereference and application crash) via a malformed YMSG notification packet, and allows (2) remote Yahoo! servers to cause a denial of service (NULL pointer dereference and application crash) via a malformed YMSG SMS message.
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.
libpurple in Pidgin before 2.7.4 does not properly validate the return value of the purple_base64_decode function, which allows remote authenticated users to cause a denial of service (NULL pointer dereference and application crash) via a crafted message, related to the plugins for MSN, MySpaceIM, XMPP, and Yahoo! and the NTLM authentication support.