MDNS is not safe against malformed or short packets

[matthewgream]

The buffer is allocated according to the size of the packet:

ArduinoMDNS/MDNS.cpp

Line 532 in 00ed2b6

udpBuffer = (uint8_t*) my_malloc(udp_len); //allocate memory to hold _remaining UDP packet

• but buffer is accessed based upon apparently number of queries in the packet header
• and butter is accessed and offsets are increased without ensuring that end of buffer is not overrun
• therefore, trivial ability to denial of service ArduinoMDNS devices with malformed UDP packets causing illegal instruction accesses