contrib.sessions.middleware.SessionMiddleware in Django 1.8.x before 1.8.4, 1.7.x before 1.7.10, 1.4.x before 1.4.22, and possibly other versions allows remote attackers to cause a denial of service (session store consumption or session record removal) via a large number of requests to contrib.auth.views.logout, which triggers the creation of an empty session record.

The (1) contrib.sessions.backends.base.SessionBase.flush and (2) cache_db.SessionStore.flush functions in Django 1.7.x before 1.7.10, 1.4.x before 1.4.22, and possibly other versions create empty sessions in certain circumstances, which allows remote attackers to cause a denial of service (session store consumption) via unspecified vectors.

The session backends in Django before 1.4.21, 1.5.x through 1.6.x, 1.7.x before 1.7.9, and 1.8.x before 1.8.3 allows remote attackers to cause a denial of service (session store consumption) via multiple requests with unique session keys.