The dissect_pw_eth_heuristic function in epan/dissectors/packet-pw-eth.c in Wireshark 1.6.x before 1.6.13 and 1.8.x before 1.8.5 does not properly handle apparent Ethernet address values at the beginning of MPLS data, which allows remote attackers to cause a denial of service (loop) via a malformed packet.
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.