View at Official ubuntu advisory, NVD, CVE.org · CVE detail
Freshness: upstream tracker timestamp is available; use API updated time as primary recency signal.
CVE-2017-8900 medium priority: Ubuntu including 1 source packages (lightdm), 5 status rows across 5 suites (trusty, upstream, xenial, yakkety, zesty): released 2, DNE 1, needs-triage 1, not-affected 1.
LightDM through 1.22.0, when systemd is used in Ubuntu 16.10 and 17.x, allows physically proximate attackers to bypass intended AppArmor restrictions and visit the home directories of arbitrary users by establishing a guest session.