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.