X.Org is X.Org Foundation's public implementation of the X Window System.
X.Org miscalculates the size of a buffer in the XRender extension.
An X.Org user could exploit this issue to make the X server execute arbitrary code with elevated privileges.
There is no known workaround at this time.
All X.Org users should upgrade to the latest version:
# emerge --sync
# emerge --ask --oneshot --verbose ">=x11-base/xorg-x11-6.8.2-r7"