cvs history -acf path/to/file | sort
By default, CVS will not show it for all users (a) and also not on all modifications (commits, c). The results are not always in chronological order, so sort them.
CVS log prints the information that was entered to describe the update:
cvs log path/to/file
To compare to another revision:
cvs diff -r 1.44 -r 1.45 path/to/file