Debian Security Advisory 1288-1 – It was discovered that the PoPToP Point to Point Tunneling Server contains a programming error, which allows the tear-down of a PPTP connection through a malformed GRE packet, resulting in denial of service.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/56603/dsa-1288-1.txt
Source: https://packetstormsecurity.com/files/56603/Debian-Linux-Security-Advisory-1288-1.html