Fix Buffer Overflow Vulnerabilities in Firmata SYSEX Message Processing

[arche8]

Bug Description

When processing oversized SYSEX messages, buffer overflow occurs due to missing bounds checks in processSysexMessage() and decodeByteStream(). For example, when sysexBytesRead = 148 but dataBufferSize = 64, the system attempts to process 147 bytes of data in a 64-byte buffer(https://github.com/firmata/arduino/blob/main/FirmataParser.cpp#L448). This causes memory corruption by:

• Writing beyond dataBuffer boundaries in decodeByteStream()
• Overwriting the dataBuffer pointer itself through out-of-bounds writes
• Causing system crashes when the corrupted dataBuffer pointer is dereferenced

Proposed Fix

Ensure decodeByteStream() only processes data that actually exists within dataBuffer bounds by using min(sysexBytesRead - offset, dataBufferSize - offset) in processSysexMessage function.