net/packet/af_packet.c in the Linux kernel before 2.6.39.3 does not properly restrict user-space access to certain packet data structures associated with VLAN Tag Control Information, which allows local users to obtain potentially sensitive information via a crafted application.
https://github.com/torvalds/linux/commit/13fcb7bd322164c67926ffe272846d4860196dc6
https://bugzilla.redhat.com/show_bug.cgi?id=728023