net/xfrm/xfrm_policy.c in the Linux kernel through 4.12.3, when CONFIG_XFRM_MIGRATE is enabled, does not ensure that the dir value of xfrm_userpolicy_id is XFRM_POLICY_MAX or less, which allows local users to cause a denial of service (out-of-bounds access) or possibly have unspecified other impact via an XFRM_MSG_MIGRATE xfrm Netlink message.

A flaw was discovered in gdm 3.24.1 where gdm greeter was no longer setting the ran_once boolean during autologin. If autologin was enabled for a victim, an attacker could simply select 'login as another user' to unlock their screen.