The KDE team fixed a bug in kppp in 2002 which was now discovered to be exploitable by iDEFENSE. By opening a sufficiently large number of file descriptors before executing kppp which is installed setuid root a local attacker is able to take over privileged file descriptors.
For the stable distribution (woody) this problem has been fixed in version 2.2.2-14.7.
The testing (sarge) and unstable (sid) distributions are not affected since KDE 3.2 already contained the correction.
We recommend that you upgrade your kppp package.