All versions of l2tpd contain a bss-based buffer overflow. After circumventing some minor obstacles, the overflow can be triggered by sending a specially crafted packet.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/33490/l2tpd.txt
Source: https://packetstormsecurity.com/files/33490/l2tpd.txt.html