ip_nat_pptp in the PPTP NAT helper (netfilter/ip_nat_helper_pptp.c) in Linux kernel 2.6.14, and other versions, allows local users to cause a denial of service (memory corruption or crash) via a crafted outbound packet that causes an incorrect offset to be calculated from pointer arithmetic when non-linear SKBs (socket buffers) are used.
kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git%3Ba=commitdiff%3Bh=03b9feca89366952ae5dfe4ad8107b1ece50b710
secunia.com/advisories/18482
securityreason.com/securityalert/388
www.securityfocus.com/bid/16414
www.trustix.org/errata/2006/0004
www.vupen.com/english/advisories/2006/0220
exchange.xforce.ibmcloud.com/vulnerabilities/24204