Debian Security Advisory 1106-1 – Marcus Meissner discovered that the winbind plugin in pppd does not check whether a setuid() call has been successful when trying to drop privileges, which may fail with some PAM configurations.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/48167/dsa-1106-1.txt
Source: https://packetstormsecurity.com/files/48167/Debian-Linux-Security-Advisory-1106-1.html