Ray Strode of Red Hat reports:

Clutter contains APIs for recognizing finger and mouse movement based gestures. GNOME Shell uses these APIs to recognize when the user lifts the "screen shield" to initiate the screen unlock process (where a password would normally be entered).

A bug in clutter's gesture handling code leads to a crash in some cases when the user performs gestures. This crash can lead to screen lock bypass. The bug was fixed upstream in clutter 1.16.2

External reference: https://bugzilla.gnome.org/showbug.cgi?id=749847

A security flaw was found in the way Clutter, an open source software library for creating rich graphical user interfaces, used to manage translation of hierarchy events in certain circumstances (when underlying device disappeared, causing XIQueryDevice query to throw an error). Physically proximate attackers could use this flaw for example to obtain unauthorized access to gnome-shell session right after system resume (due to gnome-shell crash).

Upstream bug: [1] https://bugzilla.gnome.org/showbug.cgi?id=701974

References: [2] http://www.openwall.com/lists/oss-security/2013/06/18/7 [3] http://www.openwall.com/lists/oss-security/2013/06/19/1

Relevant upstream patch: [4] https://git.gnome.org/browse/clutter/commit/?h=clutter-1.14&id=e310c68d7b38d521e341f4e8a36f54303079d74e (against clutter v1.14) [5] https://git.gnome.org/browse/clutter/commit/?h=clutter-1.16&id=d343cc6289583a7b0d929b82b740499ed588b1ab (against clutter v1.16)