An authenticated user without any specific authorizations may be able to repeatedly invoke the features command where at a high volume may lead to resource depletion or generate high lock contention. This may result in denial of service and in rare cases could result in id field collisions.
bson/cbsonmodule.c in the mongo-python-driver (aka. pymongo) before 2.5.2, as used in MongoDB, allows context-dependent attackers to cause a denial of service (NULL pointer dereference and crash) via vectors related to decoding of an "invalid DBRef."
MongoDB before 2.0.9 and 2.2.x before 2.2.4 does not properly validate requests to the nativeHelper function in SpiderMonkey, which allows remote authenticated users to cause a denial of service (invalid memory access and server crash) or execute arbitrary code via a crafted memory address in the first argument.