There is an illegal address access at asm/preproc.c (function: is_mmacro) in Netwide Assembler (NASM) 2.14rc16 that will cause a denial of service (out-of-bounds array access) because a certain conversion can result in a negative integer.
Netwide Assembler (NASM) 2.14rc16 has a heap-based buffer over-read in expand_mmac_params in asm/preproc.c for the special cases of the % and $ and ! characters.
Netwide Assembler (NASM) 2.14rc15 has an invalid memory write (segmentation fault) in expand_smacro in preproc.c, which allows attackers to cause a denial of service via a crafted input file.