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A link peer can advertise an excessive node count that later expands a communication RAM copy beyond its fixed buffer. Enforce the configured game topology, reject premature data packets, and validate send and receive layouts before accessing communication RAM.
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A Naomi link peer can advertise an excessive node count in a UDP Start packet:
NaomiM3Comm::receiveNetworklater combines that count with the game’s communication slot size and copies the result into a fixed 128 KiB buffer:The node count and destination range are not validated. With link networking enabled, a malicious peer can follow the forged Start packet with a Data packet and cause the copy to overwrite memory beyond
comm_ram, crashing or corrupting Flycast.Enforce each supported game’s configured node limit, validate SyncReply and Start topology data, and ignore Data packets received before the network starts. Also validate inbound and outbound communication-RAM layouts against the protocol’s packet limit and the fixed buffer capacity before accessing memory.