The ip6_append_data_mtu function in net/ipv6/ip6_output.c in the IPv6 implementation in the Linux kernel through 3.10.3 does not properly maintain information about whether the IPV6_MTU setsockopt option had been specified, which allows local users to cause a denial of service (BUG and system crash) via a crafted application that uses the UDP_CORK option in a setsockopt system call.