The connection_edge_process_relay_cell function in or/relay.c in Tor before 0.2.3.25 maintains circuits even if an unexpected SENDME cell arrives, which might allow remote attackers to cause a denial of service (memory consumption or excessive cell reception rate) or bypass intended flow-control restrictions via a RELAY_COMMAND_SENDME command.
Exploitability
AV:NAC:LAu:NImpact
C:NI:NA:P5/AV:N/AC:L/Au:N/C:N/I:N/A:P