A protocol parser is code that reads network messages and turns raw bytes into structured data the application can use. In security terms, it is a trust boundary: the parser must handle anything an attacker can send, not just well-formed traffic. If it miscalculates lengths, trusts fields too early, or writes past allocated memory, the result can be a crash, data corruption, or code execution.
Protocol parsers are high-value targets because they sit directly between the network and the program’s memory. Attackers often target them by sending malformed packets, oversized fields, or unexpected state transitions. Defenders reduce risk by validating every length and type, using safe memory handling, fuzz testing parsers with bad inputs, and disabling unneeded protocol features. In remote desktop tools, clipboard or channel parsers are especially sensitive because a malicious server may feed hostile data into the client.