Thanks for the comments.

The exploit you pointed out, requires a user to have root privledges to be able to break out of the Jail. The only point where root priveldges are used is when suExec performs the user change and the chroot which is done via a SUID bit.

SuExec prevents changing to a user with a GID/UID < 100, so as long as suExec is secure (which, due to it's simplicity it ususally is), that exploit should be blocked off.

As for the modperl users tip, I shall go post this question there now.

James Austin.