There must be more context to that. CVS doesn't have change sets; just from looking at this log, we don't know what else may be related to this.
Maybe some important shell scripts hang in a loop because they expect head to report an unsuccessful termination status when a file doesn't exist. Maybe some situation exists where a privileged system script can be fooled into looping by an unprivileged user.
http://cvsweb.openbsd.org/cgi-bin/cvsweb/src/usr.bin/head/he...
You're one click away from the diff.