Yes. Look at the verifymsg trigger script.
http://ximbiot.com/cvs/manual/cvs-1.11.21/cvs_18.html#SEC170
Also of possible interest:
CVS Annotate or FORCING user to comment their checkins
http://lists.gnu.org/archive/html/info-cvs/2005-05/msg00136.html
An example verify_checkin.sh script is provided here:
http://lists.gnu.org/archive/html/info-cvs/2000-11/msg00330.html
to look for a bug number and some commit comments.
If you write a script that looks at the command-line argument filename
with a log message in it and determines if it passed your criteria, then
have it 'exit 0' in that case and exit with non-zero return code if it
fails.
A very simple script might be the following Bourne Shell script that
asks the 'wc' command to cound the number of words in the log message
if the number is zero, it will fail the commit after printing a
"You need to enter a log message." text for the user:
------- cut here -------
#! /bin/sh
[ `wc -w < $1` -eq 0 ] && { echo You need to enter a log message.; exit 1; }
exit 0