X.Org Xfont library.
It was discovered that libXfont incorrectly followed symlinks when opening font files.
A local unprivileged user could use this flaw to cause the X server to access arbitrary files, including special device files.
There is no known workaround at this time.
All LibXfont users should upgrade to the latest version:
# emerge --sync
# emerge --ask --oneshot --verbose ">=x11-libs/libXfont-1.5.4"
All LibXfont2 users should upgrade to the latest version:
# emerge --sync
# emerge --ask --oneshot --verbose ">=x11-libs/libXfont2-2.0.3"