The (1) roaming_read and (2) roaming_write functions in roaming_common.c in
the client in OpenSSH 5.x, 6.x, and 7.x before 7.1p2, when certain proxy
and forward options are enabled, do not properly maintain connection file
descriptors, which allows remote servers to cause a denial of service
(heap-based buffer overflow) or possibly have unspecified other impact by
requesting many forwardings.

mdeslaur