An integer underflow vulnerability exists in the `nextstate()` function in `gpsd/packet.c` of gpsd versions prior to commit `ffa1d6f40bca0b035fc7f5e563160ebb67199da7`. When parsing a NAVCOM packet, the payload length is calculated using `lexer->length = (size_t)c - 4` without checking if the input byte `c` is less than 4. This results in an unsigned integer underflow, setting `lexer->length` to a very large value (near `SIZE_MAX`). The parser then enters a loop attempting to consume this massive number of bytes, causing 100% CPU utilization and a Denial of Service (DoS) condition.

gpsd before commit dc966aa contains a heap-based out-of-bounds write vulnerability in the drivers/driver_nmea2000.c file. The hnd_129540 function, which handles NMEA2000 PGN 129540 (GNSS Satellites in View) packets, fails to validate the user-supplied satellite count against the size of the skyview array (184 elements). This allows an attacker to write beyond the bounds of the array by providing a satellite count up to 255, leading to memory corruption, Denial of Service (DoS), and potentially arbitrary code execution.