LibXfont is the X.Org font library. TightVNC is a VNC client/server for X displays.
The libXfont code is prone to several integer overflows, in functions ProcXCMiscGetXIDList(), bdfReadCharacters() and FontFileInitTable(). TightVNC contains a local copy of this code and is also affected.
A local attacker could use a specially crafted BDF Font to gain root privileges on the vulnerable host.
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-1.2.7-r1"
All TightVNC users should upgrade to the latest version:
# emerge --sync
# emerge --ask --oneshot --verbose ">=net-misc/tightvnc-1.2.9-r4"