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 product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.