libwmf is a library for converting WMF files.
The embedded fork of the GD library introduced a "use-after-free" vulnerability in a modification which is specific to libwmf.
A remote attacker could entice a user to open a specially crafted WMF file, possibly resulting in the execution of arbitrary code with the privileges of the user running the application, or a Denial of Service.
There is no known workaround at this time.
All libwmf users should upgrade to the latest version which no longer builds the GD library:
# emerge --sync
# emerge --ask --oneshot --verbose ">=media-libs/libwmf-0.2.8.4-r3"