Bro 2.5.4 primarily fixes security issues
Multiple fixes and improvements to BinPAC generated code related to array parsing, with potential impact to all Bro's BinPAC-generated analyzers in the form of buffer over-reads or other invalid memory accesses depending on whether a particular analyzer incorrectly assumed that the evaulated-array-length expression is actually the number of elements that were parsed out from the input.
The NCP analyzer (not enabled by default and also updated to actually work with newer Bro APIs in the release) performed a memory allocation based directly on a field in the input packet and using signed integer storage. This could result in a signed integer overflow and memory allocations of negative or very large size, leading to a crash or memory exhaustion. The new NCP::max_frame_size tuning option now limits the maximum amount of memory that can be allocated.